Basically, you start an emacs server instance, then open emacs client frames/buffers for your shells.

You can split the frame like tmux, and you can “detach” your client windows, while leaving the emacs server running with your shells and anything that you are running in the shells still active.

If you’re already spending a lot of time in emacs, this works quite nicely. If not, I opine that it’s better to just use tmux or screen.