MAME will emulate several terminals. Among them is the vt240.

Here are my links for roms and docs:

http://www.bitsavers.org/pdf/dec/terminal/

https://github.com/larsbrinkhoff/terminal-simulator/issues/1

https://www.mail-archive.com/[email protected]/msg09086...

https://forums.bannister.org/ubbthreads.php?ubb=showflat&Num...

https://simh.trailing-edge.narkive.com/qgzCvrl8/dec-vt-emula...

I have a bunch of PDFs in along with this, and a vt240.zip that must have come from one of the above.

I also used this command line call to get the terminal running with "bitbanger."

  mame -rp . vt240 -window -nothrottle -host null_modem -bitb socket.localhost:2323