The rules state that all officially released sources are accepted, does that include critical role content
Manly is it possible to play a bloothunter in VALUE?
No, critical rolecontent is not allowed unless it got published in an official book - so far this is true only for Explorer’s Guide to Wildemount.
To add to that, some DMs might allow it, if you ask. But you would not have a guarantee that you can take that character from game to game like you would with a “legal” one.
I allow Bloodhunter at my table, but as stated above, always check with the DM before hand.
All officially released resources such as printed books (like PHB, MPMM, ERLW, MOT,
VRGR, XGtE, … ) and material officially released for Adventurer’s League (like ALCoS, ALEE, ALRoD, …) are allowed. You can use stuff from all these resources without restriction.
You cannot use playtest material (such as Unearthed Arcana), homebrew and 3rd-Party materials.
so as @Arthilas correctly stated, the Explorer’s Guide to Wildemount (e.g. Echo Knight fighter) would be fine
Call of the Netherdeep would also work at any table (e.g. if a DM wants to drop a magic item from that book)
on the other hand:
Tal’Dorei Setting Reborn (e.g. College of Tragedy bard) would not be fine
… unless a DM allows it as a Homebrew Award … sadly such a character would not be playable at other tables
Main problem would be such a character would only to be allowed to play at your table … which would defeat the purpose to be able to play your characters at any V.A.L.U.E. event.
… same would be true if a DM would allow a player a homebrew race or subclass
Ihmo adding homebrew spells that only work at your table is a far easier, since such a character can still play (without casting such spells) somewhere else.
(examples here and here)