Hi,
Thanks for the report.
Confirmed issue, we’ll resolve for v6.10.
Basically we need to change the GMrender advertised UUID per system.
In the service /etc/systemd/system/gmrender.service, add the entry -u system1
gmediarender -u system1 -f DietPi-device1 --gstout-audiodevice=sysdefault --gstout-initial-volume-db=-1 --logfile=/var/log/gmrender.log
systemctl daemon-reload
dietpi-services restart
Do the same on the other system, changing -u system1 to -u system2
You should now see both devices in any DLNA client.