See Juuxel/VanillaParts#29 for the crash log. The issue is basically that MoreCulling @Overwrites Block.shouldDrawSide while LibMultipart tries to inject into it:

https://github.com/fxmorin/MoreCulling/blob/8fbbec7077bde4c7198f9c238b29e09179c41c96/src/main/java/ca/fxco/moreculling/mixin/Block_drawSideMixin.java#L23-L25

The next version will have an API with instructions on how to use it.

I'm still waiting for LibMultipart to either merge or close the 1.19 pull request so that I can make my compatibility

Does not seems to crash anymore. Tried with latest backport for 1.18.2.

As mentioned here: AlexIIL/LibMultiPart#50
It will not crash but it will also not work as intended for LibMultipart