Sideload OTA not working

[gpvecchi]

I always used it to load updates, I can't succeed with Android 11 DP2.1
Deamon is started, adb devices shows the phone, but sideload fails with:
adb: sideload connection failed: closed
adb: trying pre-KitKat sideload method...
adb: pre-KitKat sideload connection failed: closed

Suggestions, please?