For years (decades) I have ssh'd in and vim'd and tmux'd my way to success. This has been great, and I still love it as a way to work. Last two days my desktop has been turned off (home maintenance has necessitated I move it), and I've been using repl.it for Advent Of Code. Which is awesome.
It made me curious about the maturity of open source self-hosted versions of the same thing. It looks like they're very mature.