Current in-testing Unearthed Arcana options are allowed by my books.
I also tentatively allow certain options from DMs Guild, En5ider, and D&D Beyond, but those are really on a review basis. Even beyond balance concerns, I don't like the idea of overlapping subclass themes within the same class. If it's an archetype of the class, it should be able to stand out from the crowd and be its own thing. Death & Grave (and also Twilight & Trickery) Domains are already too close for comfort before allowing things like Entropy Domain from Ruins of Mezro & Xanathar's Lost Notes to Everything Else, especially now that we also have UA options for swapping out Divine Strike for Potent Cantrips in the Variant Class Features playtest.
Some classes I'm more courteous with because they just don't have enough options in RAW+UA - say Artificer or Ranger (but again, a lot of those options published are working off of bad versions of those base classes, like the PHB Ranger or the 2018 Artificer). I'll allow PHB Ranger, mind you, but I strongly urge folks to use the Variant Class Features Ranger instead.