I might not manage to actually explain that well or do the report correctly since its my first time, sorry about that.

I'm playing with a few friends on a Modded server (hosted by Aternos) since three weeks by now and we added the mod recently (a few days ago). but the ores wont spawn anywhere, even in new chunks that we generate

we use a lot of mods (around 73 counting the APIs and QOL mods) but the two mains ones that modifies terrains are Better End and Regions Unexplored.

Don't know if its a bug, but I felt like it would be a good idea to report it incase

Looking at the tags both Regions Unexplored and Better End should work just fine. Considering you are using Aternos - make sure the mod was installed correctly