[zeendo]

If you can't install screen then I'm surprised you can install tmux - BUT if you can install wezterm then it solves this need nicely by adding sessions + multiplexing to the terminal emulator itself.

https://wezterm.org/multiplexing.html

[aragilar]

tmux is probably already there (ubuntu always includes it), wezterm won't be. If I need to connect to a random machine, I first try tmux, then byobu, then screen. If one of those is not there it's most likely a fairly weak machine and so it's unlikely that anything can be installed on it.