The softlink goes away when the RPi is rebooted. If it is recreated immediately after reboot, all 3 platforms were able to respond with data to 'gpsmon /dev/gps'. The Astroberry was also able to report GPS data with the Indi Control Panel. But the 2 Stellarmate platforms did not report GPS data in the Indi Control Panel.
[edit]
This behavior has been consistently confirmed over multiple reboot cycles.
This file was missing:
/lib/udev/rules.d/60-gpsd.rules
Recreating the file with this in it fixed the problem:
SUBSYSTEM=="tty", ATTRS{idVendor}=="1546", MODE="0666", SYMLINK+="gps", TAG+="systemd", ENV{SYSTEMD_WANTS}="gpsdctl@%k.service"
Followers of this topic may find this interesting - from CISA, the government cybersecurity agency: us-cert.cisa.gov/ncas/current-activity/2...on-gpsd-rollover-bug. The fix rolled out this week -- may want to be sure that you are running the latest version of GPSD (3.23), or newer.
Jon