I’m a college professor in the humanities (religious studies, history). Got into linux about 5 years back, partly because it comports better with my lefty politics than the alternatives, but also just because I’ve long been a closet computer nerd. I currently run a couple of proxmox servers on old optiplexes I grabbed off ebay. Full *arr stack with jellyfin on docker, a Tails VM for TOR stuff, NAS (omv on a vm), some other dockerized stuff: linkding, radicale, alexandrite (a self-hosted lemmy client, which I’m currently writing this on), various backup utilities.
It’s basically just a hobby for me, though the switch to linux has also totally changed my academic workflow, e.g. I do all my writing in nvim + latex now, use syncthing to sync my home desktop, laptops, and office computer, etc. I dig divesting myself from corporate computing to the greatest extent possible, appreciate the privacy benefits, and generally just enjoy the community-driven spirit of the whole thing.
You say this machine is headless. Is it at a remote location? If not, is it feasible to connect it to a monitor an keyboard for a few minutes? If so then you could logout, switch DE, and then log back in. That would hopefully set the DE you prefer as user default.
If that’s not possible, then some of the solutions discussed here might be applicable.