I'd be honest, my approach is "everything is utf-8, right? And every terminal has at least 16 colors at the ready?". It does not degrade gracefully, I checked. It's more of a party trick than something reasonable, but nothing stops you from doing it correctly, it would just be a hassle to serve in a static way (every variation would require a different txt file to be generated and sent).
Very strange, I could have sworn I've tested in without -R with Debian 11 (I can't check, that laptop broke and my other machines are still at 10). Maybe it's terminal definition or something changed.
Terminal emulation is a spooking place full of ancient magic. One of the reasons why I assumed "modern defaults". It would turn "a weekend hack" into a session of misery. ;)
> EDIT: doesn't work when piping to less.
try -R