Basically what the title says.
Im using 1.16.5, Mod Version 0.5

Im not getting any crashlogs so here's the latest log:
https://gist.github.com/Asveste/0962ed306d8a745cb31f4f679a24e3c4

Hey!
I tried to reproduce it right now and the newest mod release (Version 0.7) seems to have fixed the issue, as I was able to start the game without any problems.

Can this be recreated in a clean instance

Optifine
So that's why, easy enough fix, stop using it

Hello! I had the same problem in 1.16, crashing on startup even with the latest version of the mod:

I only added geckolib and this mod, then this is part of the crash report:
https://gist.github.com/masonclomid/e9205a470fbe542bf40ebcc5da229878