We’ll see what they tell you, but in my opinion they won’t be able to help you with this, it’s still a Domadoo reseller ^^
If you want to contact someone, here it would be more the Zigbee2mqtt community (which I remind you is a separate project from Gladys, just like Node-RED), they have a community here:
By the way, I have this dongle @Jluc, and I did a reinstallation of Gladys no later than last week to test the Bullseye image ([Recherche de testeurs] Nouvelle image Gladys Raspberry Pi OS sous Bullseye - #50 par pierre-gilles), and everything was working for me (Raspberry Pi 3B+, Sonoff 3.0 USB key bought at Domadoo as well).