You'll find info on Pi Doors here (Agency) posted multiple times by various people to this area (Mystic BBS Support). Use T for search and Doors. As you walk though Mystic BBS support searching for doors you'll find all kinds of information in this FSX_MYS area. There are two main
Pi Door setups: qemu setup & DOSBox setup. Gryphon was the first to
write up using qemu with FreeDOS image. It will work on Pi B on up.
Faster newer Pi can use DOSBox. Gryphon's method was based on a couple
of older setups: https://en.wikibooks.org/wiki/QEMU/FreeDOS http://how-to.wikia.com/wiki/How_to_install_FreeDOS_in_QEMU
Not sure where the message(s) for this are at present, but they are here on Agency multiple times. One of the first was from 2016 and reposted by Skuz on 09-09-17 00:47. Should be around message 1815 from start of FSX_MYS 09 Jan 17 14:12:00 from Avon to All titled:
Subj : Re: Run DOS BBS DoorGames on the Raspberry Pi
To get things from here on most Pi you open another Shell (Control-T)
and use the mouse to highlight areas, then Control-SHIFT-C to capture and Control-Shift-V to paste. That should work in both directions.