I make 3d Avatars for VR applications like VRChat and VSeeFace as a hobby.
You can view them on Gumroad and Itch.

The single relevant format for VR & V-Tubing avatars is a .unitypackage that contains a scene with a setup somewhere.
There is no interoperability for avatars. And it is severely lacking for 3d models by themselves.
Using those avatars as an end-user is prohibitively difficult as it requires the use of a Game-Engine like Unity.

I'm trying to improve that, by creating a truly extensible file-format for 3d models, with the capability to be easily extended with VR avatar components, that is agnostic of any game-engine or application.
You can view my progress in the STF - Scene Transfer Format Repository

Find all my links at mars.squirrel.pub.