I know in current editions they don't explicitly state that the auras for paladins are based on magic.
I haven't ran into this yet, but my question is, does the effect provided from an aura penetrate anti-magic?
As you imply, anti-magic affects "spells and magical effects". Spells are obvious. Magical effect means an effect created/sustained by magic - either a spell or magic item.
D&D 5e says what it means and means what it says: unless an ability is called out as magical or a spell then it is neither.
The paladin's aura is not identified as magical so it isn't and is unaffected by an antimagic zone. Neither is their ability to lay on hands, however, a Potion of Healing is because it is a "magical red fluid" or a Cure Wounds spell is because its a spell.
Indeed, most class features are not magical in any way. Exceptions include:
Determining whether a game feature is magical is straightforward. Ask yourself these questions about the feature:
- Is it a magic item?
- Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
- Is it a spell attack?
- Is it fueled by the use of spell slots?
- Does its description say it’s magical?
Since the answer is No to each of the questions, a Paladin's aura would not be considered magical.