I used LinuxDeploy, which is seriously outdated by now, but it works and it’s easy to use.
You just need to update the chrooted Linux from e.g. Ubuntu 18.04 to something modern. But that’s not too hard.
It could be possible to load phosh. I didn’t manage to get Gnome running (which phosh is based on afaik). But I guess if your Linux-fu is a bit better than mine, you might be able to get it to work.