https://gist.github.com/malte0811/00260bb4ce89f9b42d43fd98d2209c84
While joining a dedicated server. ImmersiveEngineering-1.16.1-3.1-c1074723.jar

Still happens on 1.16 as discussed on Discord

Fixed again in 4ad3a9b

Will Arc Recycling recipes show up in JEI still?

No. I can probably throw another if (singleplayer) in there somewhere, but that would obviously only work in singleplayer. For dedicated servers I think the only option is to sync the recipes.