I know how to set limits per user:
systemctl set-property user-1000.slice CPUQuota=5%
However, I don't know how to set the limit for a group of users. I want to limit the sum of the CPU usage of all the users in a specific group.
I also tried cgroup-tools, but I found it not usable on Debian. After installing, I even couldn't find cgred or cgconfig in systemd.