Requirements:
- Must be more user friendly than LFS
- Must not be in the RHEL/IBM family/stream or derivative
- Must not be SLES or derivative
- Does not make you install a desktop environment
- Must have steam
Hopes
- Rolling release
- Has a package manager of some sort
- Doesn’t require manual intervention every six months
- Maintainers aren’t psycho
The Rolling preference mostly conflicts with the ‘doesn’t require intervention’ preference. You can mitigate it somewhat by using a snapshot system like timeshift or snapper, but rolling distros by their nature are more likely to have potential problems.
Alternatively, immutable distros are kinda like a more (potentially) reliable rolling distro with built-in snapshots. Since you don’t want redhat or openSUSE based distros, that pretty much leaves perhaps Vanilla OS, but I’m not aware if they offer a headless install option.
Overall, I personally think Debian 13 checks the most boxes. It let’s you choose no DE during install, is rock solid, easily installs steam (after you enable the 32bit repos), and can be upgraded to newer major releases easily and reliably.
The only downside is it isn’t rolling, but with flatpaks and appimages for newer versions of software, the potentially older repo packages aren’t really much of an issue nowadays.
Alternatively, you can install the Steam flatpak.