Minecraft 1,21,1
NeoForge 21.1.74
ExtremeReactors2-1.21.1-2.4.13.jar
Added ExtremeReactors to the Direwolf20 FTB 1.21.1 modpack (version 1.40)

Reproduce steps:
With this modpack, yellorium should be replaced with uranium from Mekanism, and for all the Extreme Reactors recipes except the Fluidizer casing, controller, and solid injector, it works fine, including as fuel for the reactor.

Yellorium specifically is being required to craft the three recipes above and they will not show up as a valid recipe when substituting uranium. Additionally while trying to use the fluidizer itself, you are unable to place uranium into any solid injector. I was able to work around the crafting recipe issues with some kubejs scripting, but I haven't been able to add uranium to the fluidizer.