Creeper farms can be created and used in aternos servers, what do you mean?
not in my experience, every single mob farm on aternos(even with no players online) dont work, for example creeper farms, in general mob farms, like those ones where all mobs spawn, and also most mob farms that do work only work at around 5% efficiency, and never, in my entire time on aternos servers, have i ever been able to make a slime farm work, which is one of the most important things in redstone stuff. There are a lot of reasons as to why they never work, and i understand that, but i am confused as to how you are able to make them work?