Debian, unless I’m doing something specific like Home Assistant OS
Yeah, usually. The GUI uses so much system resources just to sit there and be unused. That said I do have a Windows VM for Quicken that I remote into to manage my families finances. Of course that isn’t headless.
Are you old enough to remember how Windows was? In the good old days of 95, 98, or XP?
Linux is kinda like that. Except way more capable.