I haven't had a great time with Linux on a tablet without a keyboard and mouse but PostmarketOS is 100% usable IMO. Even the on screen keyboard on the login screen works.
I don't think they need pairing. It just worked for me. It's a generic one off amazon. The Microsoft one I got with the tablet broke after a month and the replacement one also broke after a month. I'm still kind of mad about it like 4 year later.