Minecraft version: 1.16.3
Fabric Loader version: fabric-loader-0.10.2+build.210-1.16.3
Fabric API version: fabric-API-0.24.0+build.411-1.16.jar

Lastest Logs: https://pastebin.com/Dj7gKZFL
Crash Log: https://pastebin.com/fvLjZpka

Bit more testing

Test 1:

• Minecraft version: 1.16.3
• Fabric Loader version: fabric-loader-0.10.2+build.210-1.16.3
• Fabric API version: fabric-API-0.24.1+build.412-1.16
• Fabric mod menu version: mod menu-1.14.6+build.31
• Not enough crashes mod version: not enough crashes-2.1.4+1.16.2

Crash report: https://pastebin.com/fvLjZpka
Lastest logs: https://pastebin.com/HQyEQZyp

• Notes for the first test: Tested with a fresh profile on the twitch app, the crash report & latest logs look somewhat the same from the first post, tho putting it in any-ways since it's only loading the basic stuff, of the mod & the parts of the fabric that are needed. It crashes at startup, I am unable, at least on my screen, able to see any render of the loading screen starts, other than the background loading part.

Test 2:

• Minecraft version: 1.16.3
• Fabric Loader version: fabric-loader-0.10.2+build.210-1.16.3
• Fabric API version: fabric-API-0.24.1+build.412-1.16
• Fabric mod menu version: mod menu-1.14.6+build.31
• Not enough crashes mod version: not enough crashes-2.1.4+1.16.2
• • all the other mods that I normally have loaded, that's too long to list here

Crash Report: https://pastebin.com/HtJ9jw6S
Latest Log: https://pastebin.com/h05Mv596

• Notes for test 2: Running pretty much the same test as the first thread post, main modest modpack, did a check for updates & see if there are any missing bits, like lib files. turned off any other mods I know that already have a problem that leads to crashes. testing it again to see if the same type of crash happens w/ in the crash report/logs to see if it's a reproducible issue. The same happens as wrote in the notes for the first test. I do not get past the starting loading screen.

mods turned off

• • the author mod is known to cause a crash on its own, wasn't sure if I had it on or off before then I made the first post

Hey, thanks for the bug report.
Unfortunately I won't be able to make any code changes for a while. I wouldn't hold it against anyone if they made a fork, even if it would take me only a few weeks until I could update the code again.
Alternatively a fix could be made to net.fabricmc.loader.metadata.LoaderModMetadata.getEntrypoints(String) to stop returning null, in fabric loader itself.

Seems to have been an issue with Fabric Loader's json migration, a fix is open: FabricMC/fabric-loader#324. When modmuss or player has time, one of them will merge the fix and release a new build.

Something to add to this issue. Crash is caused by something with Fabric Loader 0.10.2+build.210. Not Enough Crashes works fine with Loader 0.10.1+build.209.

Java 15 seems to help explain the issue a bit more: https://gist.github.com/Diamondman121314/2f3b283bacec6f7bc284683429047a54

This should be fixed in the latest fabric build