So, about a year ago, I mused how Trick Magic Item could be really good with the new universal spellcasting proficiency. The original remaster version of the feat was identical to the pre-master version, but the errata changed that. After applying the errata, it now says
If you activate a magic item that requires a spell attack modifier or spell DC and you don’t have proficiency in the relevant statistic, use your level as your proficiency bonus and the highest of your Intelligence, Wisdom, or Charisma modifiers. If you’re a master in the appropriate skill for the item’s tradition, you instead use the trained proficiency bonus; if you’re legendary, you instead use the expert proficiency bonus.
No longer is using a better spell proficiency locked behind heavy investment into the correct skill. You can use your own! A Level 20 Wizard can cast Cleanse Affliction from a scroll using his full legendary proficiency!
But which attribut does he use to dertermine his spell attack/DC? Can he use Int for all items activated by TMI since that's the attribute linked to his class's spell proficiency?
From my reading "the relevant statistic" seems to refer to Spell Attack Modifier and Spell DC. A Wizard has both, so we ignore the rest of the paragraph.
The Wizard would use his Spell Attack Modifier and Spell DC, both of which use Intelligence, for everything they activate using Trick Magic Item.
That's my two pieces of copper, at any rate. It seems like a very nice buff.