I've just installed Ubuntu 20.04 (as a server environment, updating work infrastructure from older Ubuntu versions) and while configuring various things came across an issue I've not seen before with vi (really vim of course). Under some connection environments vi throws odd characters into the screen display - they're not saved as part of the file, they're just artefacts of the edit session. And are irritating because they mess up the screen while typing.

Using ssh from terminal running on an older Ubuntu version (18.04 based), connecting via ssh to Ubuntu 20.04 and opening a file in vi, going into insert mode puts
on screen... vi goes into insert mode fine, can type text. Ending insert mode puts another escape string up on screen - below is the effect of 'itext<esc>':


The peculiarity? I've never seen this behaviour before using any combination of OS at each end... and this doesn't happen if the 'terminal' is running in Ubuntu 20.04 (desktop) or PuTTY or Debian Buster desktop (and probably others...) , just if the terminal is running Linux Mint (couldn't get Ubuntu 18.04 to install in virtual box).