HaOS is awesome as it is just enough operating system that is necessary for Home Assistant while taking away all the hassle of managing it.
While that works great for probably all the SBCs (like Raspberries) out there the generic x86-64 flavor is another topic because of the thousands of different devices out there. Specially some old quirky intel atom based devices (which just recently got support in HaOS btw.) often have a very limited BIOS which does not allow boot specific configuration.
In my case that causes a HaOS (or default debian 11 install) to “stuck” in grub and don’t boot the OS if no display is connected. See this thread for more information Moved from supervised to haos
It looks like only one (more) parameter in the
grub cmdline is needed to overcome this situation: