?? does text display/command line only useage count as usable (vs. gui interface).
"Linux from scratch"[0] provides a way to experiement what what 'still have a usable OS' is.
IOT/ebmedded/customized OS (linux & windows) can be setup to act as a relay between local screen and remote server/cloud. There would be no backround processes/services/daemon on the local box.
0 backround processes, as long as bash comands that run as processes independent of terminal initiated from are also compiled into init & run in same process as a thread.