I recently found a PDF on DMs guild about cyberpunk D&D and didn't feel that I wanted to run it with magic. The main 3 casting classes that have a subclass in the PDF are artificer, cleric and bard. Is it possible to run D&D without magic and is it balanced? Also how would you run these classes without magic?
I've tried it now with and without magic and it does function with both. As long as no hostile creatues have magic the lack of it didn't seem game breaking.
Could you play in a post-modern setting with D&D by just using non-caster classes, non-magical feats, and redefining some of the other classes' features (like the monks ki) to be mundane powers? Probably. Would it be balanced? It's tricky.
Even fighting classes like the Barbarian subclasses come with spell-like abilities (for example, the Eagle Totem Warrior Barbarian has a flying speed from level 14, not something that you can really explain in a mundane setting). So you very likely you would be limited to Fighter and Rogue subclasses that have no spellcasting, and little else. Or you would have to come up with cyber explanations for magical effects.
A game system like 5e is a whole. Yes, there are some core mechanics, like ability scores, bonuses, how skill rolls are resolved and so on. But D&D is not d20 or gurps, or Basic Roleplaying, systems designed, or at least claiming to be, suitable for different genres of games, or malleable enough to support that sort of customization. It is an integrated whole for a fantasy setting with magic. Many features, rules and most existing classes do not make much sense any more if you remove magic. The DMG does offer some options for grittier damage, modern weapons and so on (p. 266ff), but that is a long way to a balanced game system without magic. You are going to end up reconfiguring an rebalancing the entire game, nearly as much work as making a new game.
At that point, why are you trying to do this? Why not use a game explicitly designed for cyberpunk experience, like, erm ... Cyberpunk? I think that this is going to be a better overall experience than trying to make D&D 5e be something it is not, and even with learning a new system, probably less work.
TLDR: The easy way is to cut all classes/subclasses/races/subraces that are too magical for your setting, and to fluff any remaining magic (e.g. monk ki, artificer spellcasting) as being mundane. Provided most of the problems have mundane solutions then the campaign will function, but there will be some voids in the design space (mainly mental attributes being unimportant).
The hard way is to redesign or replace all spellcasting classes with fully-featured nonmagical equivalents. This is not as simple as swapping Spellcasting for some other feature; the spellcasting classes will need to be rebuilt from the ground up or replaced entirely.
Or you could follow Groody's advice and use a different system better suited to the campaign you are trying to run.
I've run a D&D campaign without magic. It was a medieval-esque setting rather than a cyberpunk setting. The story pitted a nonmagical imperial military against a magical fey incursion, with the player characters' lack of magic providing contrast with the fey and emphasising the fantastical nature of magic.
I banned classes, subclasses, and races with overtly magical powers. This restricted the class selection to Fighters, Rogues, (Berserker) Barbarians, and some Monks (for Tier 1 and 2 you can pretend Monks are non-magical; Way of the Open Palm and Kensei are obvious choices, although a player persuaded me to allow Way of Mercy which we fluffed as acupressure and rapid first aid). Elves, forest gnomes, tieflings, and dragonborn were out, but other PHB races were fine.
The game was "balanced", in the sense that all remaining options were still viable. The campaign was successful and my players enjoyed it. However, there are a few caveats.
You obviously cannot rely on your players having any magical solutions to problems. As long as most of the problems you present to your players are mundane in nature, they should be able to use mundane solutions. But if you drop a forcecage on the party then obviously they will have a bad time.
Healing is almost non-existent outside of magic. My party had a Way of Mercy monk, and I really appreciated having a healer like that. Besides that, someone could take the Healer feat. Otherwise, you may need to homebrew some other healing solutions. I included some healing remedies which recovered hit points over a few minutes, to allow for faster healing between encounters.
You would want to be careful about using monsters which are resistant/immune to nonmagical damage. Monks can bypass this, but other classes cannot. You will want to provide another way to overcome the resistance/immunity (in my campaign, it was iron/steel, because fey), or not use that resistance/immunity.
The biggest shortfall, though, was that scrapping most of the classes meant the mental attributes (INT, CHA, WIS) were less relevant because they were not primary stats. The game still technically worked without those stats, but I could feel the asymmetry. Removing the casters left a void in the design space. If I were to run the campaign again, I would introduce some homebrew/third-party classes to fill the void (such as Kibbles' Warlord).
All these problems are a symptom of D&D having been built with magic as a ubiquitous feature. While the rules work fine without magic, and each class in 5th edition is able to stand on their own, stripping out magic leaves some big holes in the design space.
You have the benefit of working in a cyberpunk setting. Unlike my medieval-esque setting, cyberpunk has a bunch of technology which can reasonably approximate a lot of magic. Advanced technology can fill the space of magic items. Artificers already have their spellcasting flavoured as them using technology so artificers could probably be used as-is. Bards and clerics probably won't work as-is, though, so you would need to find a suitable substitute.
I'll add that I've also been a player in a steampunk Pathfinder campaign without magic (which also pitted the nonmagical people against an extraplanar magical incursion of elves). In this case the GM carefully homebrewed almost every class and race to be fully-featured without magic and to interface with the urban steampunk setting. The campaign worked excellently, but that full redesign was important, and the GM was tweaking on the fly as we tested things.
In all this, you need to consider why you are using D&D. In my case, it was because I wanted to see what happened when the players were stuck at the pointy end of the magic wand (so I still needed a magic system), and while I was running very low fantasy it was still fantasy. But running cyberpunk without magic has essentially no similarities with D&D. If all you have left is the bare bones of the mechanics and none of the genre or style, you might be better off hunting for another system which better reflects the campaign you want to run. If you still want to run D&D this way, go for it; we learn by trying. But this might be a good opportunity to branch out to another system.
Let's say it is not even remotely D&D. Let me illustrate this by taking an older edition of game: D&D 3.5. The mechanics of D&D 3.5 do make the backbone for Star Wars D20, admittedly a space-fantasy setting. I have the most experience with these two, so I take them to show how what would be a hackjob in 3.5 was entirely possible in SWd20.
Star Wars d20 is a game that plays very well without its space magic, because no class but the Jedi and Sith classes do get access to space magic at all. It bridges the lack of healing magic by offering super-potent medicine and high technology to fill in. Space combat plays some role too. So, all in all, if you don't have a force-sensitive character in SWd20, there is no obvious gap in the group. Characters are much more universalists than one trick ponies too, and the setting plays to a scoundrel game to some degree. The game also sports lots of non-force sensitive enemies of all CRs, mostly by taking a random class and one of about 100 aliens to create threats that are very varied. There's also lots of varied monsters and of course ship battles to offer variety.
Banning all magic classes for 3.5 is a considerable cut. From the base classes, everything but the fighter, barbarian and rogue are gone. Monks might still be in at the start, as they start to become all hyper-magical around lvl 4 when their fists become magical - they transcend and should thus no longer be in by lvl 10 or 11. Rangers get magic at 4 and are out. That means your party consists of very similar characters and does not bring anyone that can easily heal at all - oh, remember that in 3.5 all healing was magical or it took you ages to heal using the heal skill. Your party has almost no AoE or Group Control unless it is a group of very particularly set up rogues. Atop that, the number of non-magical enemies you could pull out of the hat is only limited to the few remaining races and classes: animals that pose a risk get rare by level 7, and everything else that is left after kicking any supernatural or magical being is most likely a character classed humanoid. Combats are prone to become exactly the same as the number of classes and races left is so low.
D&D in itself is made the be high fantasy. Sure, its engine can be used to run a dedicated game without supernatural powers, like a force-blocked game of SWd20, or a game of d20modern. But those were not just taking the existing game and cut out contents, they took the engine and totally rebuilt the entire game around it. They invented new classes, filled the gaps in tools and equipment with new gear, and all in all, made it possible to actually play the game in a way that was more than a hackjob.
Since magic is incorporated very deeply into 5E, the game would be noticeably more bare and in my opinion less interesting but you could in theory do it. Whether the result would be any good is another matter entirely. Any primarily casting classes would obviously be useless so you might as well remove them but even the non-casting classes have lots of abilities that are either magical or at least magic-like so you'd have to think about how to handle that. Bear in mind that the end result will not be balanced, you can't cut out half of the system and expect the remaining half to work like there is nothing missing.
A possible way to achieve what you're after could be to leave the mechanics as it is but reflavour spells and magic effects as technology-based and mundanely produced, e.g. a Fireball becomes a hand grenade or similar. You could do it all yourself or let the players flavour their own abilities. Depending on the technology level in your setting this might or might not be a feasible option and not all spells might work but it's easier to go through them and remove the ones that absolutely won't work rather than trying to work with a weird half-system with the basics hacked off from it.
I would, however, encourage you to at least have a look at other systems, there's lots that do not include magic by design and these will likely work much better for the story you want to tell, a lot of those are much less complex and easier to learn than D&D too. Most important, these will be balanced around no magic and designed to still be interesting to play.
