Hi - I can't speak for StellarMate but it does work with the Astroberry KStars/Ekos/Indi package. I updated the firmware in the hope that it would solve an ongoing issue with the PPB but to no avail. I am still finding that the PPB and its FTDI serial UART 'breaks' the USB port settings from time to time. So I've set up a profile called 'My Astro Gear minus PPB', I run that first, close it and then run My Astro Gear. It somehow fools the RPi into placing the EQMOD mount first and the PPB second in the Indi Tabs and all work.
Currently running KStars/Ekos/Indi on a Raspberry Pi 4B 4GByte under Raspberry Pi OS thanks to Astroberry
Sky-Watcher ED80 Pro with 0.85x FR/Corrector with Canon DSLR and ASI533MC on AZ-EQ5 GT mount
Other Sky-Watcher scopes - SkyMax 150 Pro Maksutov Cassegrain and Explorer 150p Newtonian