Windows has something called the Broadcast Driver Architecture (BDA) and virtually every ATSC tuner ever made works with it. There are several open source projects that take advantage of it, so it seems like it would be a great way to (somewhat easily) add support for a lot more tuners into Plex. Has this been looked into, and if so, is there any chance support might be added for it?
Yes you can read about the progress of some additional tuners and sign up for the beta here:
https://forums.plex.tv/categories/community-tuners
I have been in that beta and have a usb ati tv wonder 600 working well. There is a thread with ones that worked and ones that didn’t too.