Apotheosis-1.16.1-4.1.0.jar causes fatal error when loading dedicated server. Reverting to Apotheosis-1.16.1-4.0.1.jar resolves the issue. Debug log attached. See line 757:
[18Aug2020 16:44:27.262] [main/FATAL] [cpw.mods.modlauncher.TransformerClassWriter/]: Class net/minecraft/entity/IRendersAsItem unable to find resource null
debug-5.log

Well, what I can tell you is that error is right, that's a client-only class. However, Apoth does not interact with the class noted in this error, and Apoth loads fine on a dedicated server on it's own (with Placebo, JEI, and HWYLA installed). I suppose this is probably an ASM conflict between a mod with a mixin and Apotheosis, but the only ASM added in 4.1.0 was related to Crescendo of Bolts (Crossbow stuff). From the looks of it, there is another mod with a mixin into the same location, but you'd have to figure out what mod it is before any fixes can be attempted.

I am having the same issue with the latest version loading on a server i even went and made a test server with nothing but Apotheosis and i still get the same error with no other mods

umm i was looking through the code in the crossbow js file u have this here

'apothshieldblock': { 'target': { 'type': 'METHOD', 'class': 'net.minecraft.item.CrossbowItem', 'methodName': 'func_77659_a', 'methodDesc': '(Lnet/minecraft/world/World;Lnet/minecraft/entity/player/PlayerEntity;Lnet/minecraft/util/Hand;)Lnet/minecraft/util/ActionResult;' }

i was wondering if it should be like this

'apothshieldblock': { 'target': { 'type': 'METHOD', 'class': 'net.minecraft.item.CrossbowItem', 'methodName': 'func_77659_a', 'methodDesc': '(Lnet/minecraft/world/World;Lnet/minecraft/entity/player/PlayerEntity;Lnet/minecraft/util/Hand;Lnet/minecraft/util/ActionResult;)' }

I still get the same crash on a dedicated server on it's own (with, and also without Placebo, JEI, and HWYLA installed).
debug.log

Interesting, and no, that method signature is correct, it's (<params>)<return type>.
That method access appears to be attempting to resolve a class and trying to reference that client only class that doesn't exist.
That's weird because nothing in CrossbowItem even references the class in question at all.

Could anyone that is experiencing the error let me know if this fixes the issue https://github.com/Shadows-of-Fire/Apotheosis/releases/download/4.1.1/Apotheosis-1.16.1-4.1.1.jar

Launches fine for me with that one now, both alone with Placebo, JEI, and HWYLA installed, and also with all the mods I run.

Well, it's a stupid fix, but it tricks the class verifier into working right.
So I suppose it's good enough

This sounds like it's the same problem ? https://gist.github.com/MaxFirestorm/916243949f4c9356db3bd44555eccd2a

Probably a side effect of the trash hack fix, I'm waiting for cpw to let me know whats happening with the asm

This should be actually fixed in 4.1.2, this issue is apparently a modlauncher/FML bug that I have no control over, other than attempting to provide the erroneously loaded class.

The mc copy class can be removed when McModLauncher/modlauncher#57 is resolved

You should be able to remove the workaround now, the issue has been fixes in modlauncher