According to the OpenWrt wiki; Port 9100 is the default p910nd port. Port 9100 is also HP's JetDirect port and usually reserved for network printers.
How your MS computer, iOS and Andoid OS specify the destination port can vary. In the old BSD lpr print system it's 9100@ipv4 address, eg 9100@192.168.1.3. In cups it's specified 192.168.1.3:9100.
On thing you can try is to ping the printer:port to see if it's active - should be if you can print to it from your work station. What address did you specify on your Windows Work station?
Another way to test is to netcat(nc) directly to the printer and bypass the spooler:
https://docs.freebsd.org/en/books/handbook/printing/#printing-direct
For cups, you can manually specify the printer address in the config files. My phone is running GrapheneOS and I can edit some of the files. I've been meaning to set up printing but it is a low priority from a phone. My interim work around is to send the print job as an attachment to myself and print from my workstation.