I have tried to backport this bugfix,as it only appears in UI, but got this instead: 
So graphics is no longer shown at all, and white rectangle is displayed forever. Opposite of desired. Well, i think now I undestand what means "non-risky" parts. Or did I something wrong? I have literally updted to spine-unity-3.8-2021-11-10 and manually applied this 2-files commit.
Is any other option to get rid of this annoying bug. It only happens in my 4-chars rpg if I quickly switch active character and puppet is adjusted to fit current character. Maybe I can somehow prevent first frames to be drawn or like that?
upd:
Can't add 'SkeletonSubmeshGraphic' to Renderer0 because a 'RawImage' is already added to the game object!
A GameObject can only contain one 'Graphic' component.
UnityEngine.GameObject:AddComponent()
Oh, should I also reemove RawImages everywhere to make it work?
UPD2: oh now, I just restarted game 2 times and suddenly it seems to work and bug is gone. I do not need to update any RawImages in Inspector. 