Have a look at this comic:
https://wizardzines.com/comics/term/
You may notice that it references the issues that existed in the sparc
emulator. While Julia mentions setting the TERM variable to
xterm-256color, that is not likely to work on really old systems. use
vt100 for anything old. That is what the de facto standard for almost
all terminal emulators understand. You might get away with ascii, ansi,
or some others, but vt100, vt52, and a few others from the dawn of time
(well, shortly after the epoch) are what all the old systems understand.
The console on the sparc emulator has its own name which escapes my
mind, but something like sun, sun-color, sun-console, or something like
that and it is mapped to the frame buffer used with the sun monitors
that were physically wired to the systems. Terminals on the serial port
would use an appropriate setting, with vt100 being a very supported one.