APU board? They are going EOL soon, but these devices are built like a tank. Full Linux x86_64 support, coreboot bios. https://www.pcengines.ch/apu.htm A few sellers in the EU still have them.

I use a mixture of systemd-nspawn and different user logins. This is sufficient for experimentation, for actual use I try to package (makepkg) those tools to have them organized by my package manager.

Also LVM thinpools with snapshots are a great tool. You can mount a dedicated LV to each single user home to keep everything separated.