Etched crashes in Minecraft 1.16.5 when using the latest Forge release (36.2.39). This also happened with Etched 1.1.0 - it was noticed when preparing the new Valhelsia 3 update while updating Forge, and I created a clean instance to check that it wasn't caused by any mod interactions other than with Forge itself. There is a sound related change mentioned in Forge's changelog, so that'd be my initial guess as to the cause: https://maven.minecraftforge.net/net/minecraftforge/forge/1.16.5-36.2.39/forge-1.16.5-36.2.39-changelog.txt

Minecraft: 1.16.5
Forge: 36.2.39
Etched: 2.0.0 (also crashes with 1.1.0)
Pollen: 1.4.6
No other mods installed - fresh instance to reproduce this crash.

Crash Report: https://gist.github.com/Vaelzan/9dd694e3cd02f2435ac675635b5a6ba7