DankMaterialShell folks set up builds for Debian, Ubuntu and OpenSUSE, so now it's super easy to try niri & DMS on those systems.
I added Ubuntu commands to the niri quick start guide: https://yalter.github.io/niri/Getting-Started.html
Debian and OpenSUSE here: https://build.opensuse.org/project/show/home:AvengeMedia:danklinux