Can a 2019 UA Artificer use a Mizzium Apparatus as a spellcasting focus?

Question

In the 2019 Unearthed Arcana version of the Artificer, they are noted as using artisan's tools as the foci of their spells, rather than the more typical arcane or divine focuses, though the Artillerist subclass gains the ability to use rods, staves, and wands as spellcasting foci for their spells.

In the Guildmaster's Guide to Ravnica, it notes if members of the Izzet League "use an arcane focus, it probably takes the form of an intricate devices that could include metal gauntlets, glass cannisters, copper tubing, and leather straps to attach it to your body. The Mizzium Apparatus described in Chapter 5 is a magical version of this gear", and members of the Izzet League gain one for free at Faction Rank 1, which requires 3 Renown (about two adventures).

Would an Izzet Artificer be able to use a Mizzium Apparatus as their Focus if they take the Artillerist subclass, because they're proficient with the use of certain subtypes of Arcane Focus, allowing to substitute the Izzet Arcane Focus in their place?

Answer 1

As you've noted, the rules don't address this specifically. When the rules don't address something, the procedure is to ask your DM for a ruling.

(Asking rpg.stackexchange for a ruling won't help: we're not your DM, so we don't have the authority to issue house rules for your game. :) )

Most DMs will probably say: "Oh, you need an arcane focus? Sure, you can use whatever, that's fine." In D&D, the question of what sort of focus you're using is roughly as important as the question of what sort of shoes you're wearing: you're probably wearing shoes, and it would be a problem if you lost them suddenly, but it's unlikely to matter in the course of most games.

Of course, unless your DM is using unusual rules for character creation, your artificer would not be able to begin play with a Mizzium Apparatus, because that's a magic item and you can't start play with magic items.