fond memories. we did tv guides for a local cable system for a bit in the early 90s. they had a customer db, but no "export" beyond sending print jobs to their bigarse line printer.
but it was a parallel port and i had use of a luggable with a bidirectional parallel port so i'd haul that in once a month, hook it up, and have them run a "hello customer" fake billing run, which was hoovered up and stripped down to the address list we needed to mail to that month.
Have a look at the Internet Printing Protocol. I built a NodeJS app that pretended to be a printer and could receive real time transactional data from a legacy POS/software. No drivers required… supports HTTP auth… all OS’s have great support for it.
Primary use-case is to read receipt data from legacy POS systems without having to write software integrations.
Figuring out how to commercialise. Reach out if you have ideas!