Are you using vertex colors or material colors?
Can you send me VRM file?
Not sure which VRoid Studio does when I select the color in its UI.
Where can I privately sent you the .vrm (or a link), ideally?
because developers abandoned Mac and Linux platforms
I know the feeling. I've only dabbled with VTuber related software development for a little bit, but I've already had my fair share of frustration, especially because Oculus does not make its lip-syncing library available for Linux.
You can also use regular webcam for the hand tracking, it kinda works but still buggy and unfinished.
I did notice, and I've tried it - semi-successfully! I've been dying to have some hand-tracking in my setup, or support / help with some development. Currently I only know about OpenSeeFace - and it doesn't help that I'm not a big fan of Unity.
But I doubt there are more Linux VTubers.
It's possible to look up VTuber+Linux tags on Twitch, for those who use them. We can only become more numerous!