https://pastebin.com/84GgYij8 There's the full details of the crash and the mod list involved. I'm not sure if there's another mod in the list that's causing conflict with LootR's or if its just something in the lootr's forge file itself that's causing the crashes though. I figured you would know more on the matter after looking at the log though.

The error appears to be from "Relics":

Caused by: org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException: @Shadow method throwItems in relics.mixins.json:MixinPiglinAi was not located in the target class net.minecraft.world.entity.monster.piglin.PiglinAi. Using refmap relics.refmap.json

I assume this is because the Lootr chests called the PiglinAi "react to chest being opened" method.

It doesn't appear to be an issue with Lootr itself though. I'd recommend chasing up whichever mod is Relics.