Loading Ears alone does not result in any crashes, but with the other mods I have for 1.8.9, something results in a game crash. I will attempt to find which of my mods is causing it, as the crash report does not seem to mention anything but Ears,
[crash-2021-11-22_23.19.05-client.txt](https://github.com/unascribed/Ears/files/7585835/crash-2021-11-22_23.19.05-client.txt
fml-client-3.log
)

Some other mod you have installed has ASM patched the vanilla skin system in a way that Ears no longer recognizes it. My first suggestion for something to remove would be MorePlayerModels.

Wait, you have OptiFine, and MorePlayerModels doesn't show up in the coremod list at the top. Much more likely cause.

I cannot do anything for OptiFine compatibility as it is an invasive closed-source mod.

It was indeed Optifine