I am having some issues with version 1.20.1 of Fabric, as the mob drops and dungeon loots are not showing up. Is there any way to fix this? Maybe I am too noob and I also can't find the solution in the settings. I try it in single-player and on a server, and it still doesn't work

I have the same problem. However, when I leave out the other mods and just put in JEI & JER, I don't have the problem.

latest.log
Here's my log.

Could you share a log file where it doesn't load? Normally, it will have some information on which mod is breaking it.