I’d look into partitioning that server into separate droplets/containers/virtual servers.
Two decades ago (gasp, yes, it was), I had a small flock of real servers running virtual servers with this software: Overview - Linux-VServer. (This was back before every host in existence sold VPS hosting.) It was great because everyone I hosted had the ability to do whatever they needed to do as ‘root’ in their own vservers, but I could put limits on usage so they couldn’t run amok.
YMMV (it HAS been two decades), and it’s very possible there are better options now than there were then!