Don't know much about Fleet, but their accompanying space project is slowly getting better and better!
I'm liking it a lot. It isn't something particularly great yet but I like having my own domain, I like having integration with Jetbrains products, I like my own repos in a not-so-public location, I like extremely-easy-to-set-up CI.
Gitlab checks most of these boxes too but.. Dunno, Space just feels more intuitive to me. Might be due to the docs being really solid.