In a previous life I did the occasional custom home theater remote control program job. Like Harmony, but better (I think). Anyway, my personal remote is a 20 year old remote with programming software from the same era.
The connection to the pc to upload the program is a serial Jack. My small form factor pc doesn’t have room for a permanent serial card, so I use a serial to usb adapter that’s 15 or so years old.
I’ve got the drivers for all of this stuff tucked away in multiple backups, alongside .txt files with notes on how to get it all going again, when, like this week, I add new gear and need to tweak the remote.