The Devialet appearing several times in the Audio Settings is not an issue. If a device supports more than one option, e.g., Roon Ready, Devialet AIR, and Chromecast or whatever, it will show up in Settings > Audio for each of them. One user might prefer Devialet AIR and another Roon Ready, for instance.
You canāt delete them because then how would you later switch to another variant if you want? This is the Audio Settings configuration, it shows everything that is available from your devices. Just donāt enable the variants you donāt need and forget about it.
Any device / variant that you enable here in the Audio Settings you can then choose from the zone output button. If you enable two variants for your device, you can choose either as a zone. Should normally not hurt but clutters up the zone menu.
The actual issue you are having is most likely a network configuration issue. See for instance this thread about āDevice in useā errors with Devialet: