Copy-pasting u/marimbaguy715 from the Reddit page discussion:
For those who don't want to read it, it's fairly similar to the Tasha's class. Changes include:
- Magical Tinkering crafts distinct items from a list
- Infusions/Replicate Magic Item has changed in flavor but is very similar in function. You now no longer infuse non-magical items to make them magical, you're always replicating magic items. But all of the old infusions are included as magic items (if they don't already exist as magic items, like +1 Armor for Enhanced Defense). The major change here is that there are way more potential magic items you can make, as it gives you broad categories to pick from (e.g., at level 6, you can make any Uncommon Armor/Wand/Weapon that isn't cursed).
- Flash of Genius now lets you know if a check or save succeeded or failed before you use it
- Spell-Storing Item can go up to level 3 now, rather than level 2
- Soul of Artifice's Cheat Death was changed slightly, and you no longer are going to get a +6 to all saves (instead you get +1d6 to all ability checks)
- Alchemists' get more potions, those potions are Bonus Actions, the Alter Self potion is gone (replaced by a "choose any other effect" in the random table), the subclass has a few numerical boosts, and at 15th level can cast Tasha's Bubbling Cauldron 1/day for free
- Armorer has a new option called Dreadnought that does more damage, has reach, can make you Large (and later huge), and can push around creatures. Other options got numerical buffs.
- Artillerists' Eldritch Cannon can choose their option each turn rather than being stuck on one option for the whole fight
- Battle Smiths' Steel Defender got numerical tweaks
- All subclasses can craft items related to their subclass faster (Alchemist - Potions, Artillerist - Wands, Armorer - Armor, Battle Smith - Weapons)
It didn't get sweeping changes, but since it's a recent class I don't think that should be too surprising. I'm hoping this means we might see a return to Eberron soon, but it's equally possible this just gets put in the first Xanathar/Tasha-esque book.