I run plenty of services in my lab on k3s. Most of them I had to manually build charts for and add them to my cluster. I doubt anyone has built charts for Lemmy, maybe mastodon. Anything that's dockerized like Lemmy can be put into kubernetes, but it's going to take some doing. Good luck out there, and of course if you get it working then I think the maintainers would be happy to get a helm chart merged into their repo.