See if they’re overlapping, do a survey with your phone and WiFiAnalyzer (or another app). If they’re close or overlapping, set the router to a fixed channel as well.
Also, true story, LTSC 2019 can’t see shares from LTSC 2021, but the opposite works without a problem 🤣. It was a bug, they eventually fixed it, but took them like a year or so (they threw the ball at users, not setting up the shares correctly 😒), and I already reinstalled all rigs with LTSC 2019, so… too late MS 🤷… I haven’t used LTSC 2021 from that point on.
Try searching online for cups filters. Maybe someone made a custom filter file for that printer that works… worth a shot 🤷. I’ve had luck hunting down custom filters for some obscure printers in the past.
Setting up a shared printer in Windows is (could be) a PITA though… not being able to choose SMB versions can make your Linux setups with SMB a pain 😔. That’s why I prefer Linux with samba as the print server, you can fine tune almost everything to make it work with any Windows and Linux install.