Actually, my tests were not much successful.... 
I managed to pair Shelly Gen4 1PM just once :
Manufacturer: Shelly
Endpoint 01 endpointId: 01
Endpoint 01 idAsInt: 1
Endpoint 01 inClusters: 0000,0003,0004,0005,0006,0B04,0702
Endpoint 01 initialized: true
Endpoint 01 manufacturer: Shelly
Endpoint 01 model: 1PM
Endpoint 01 profileId: 0104
Endpoint 01 stage: 4
Endpoint EF application: unknown
Endpoint EF endpointId: EF
Endpoint EF idAsInt: 239
Endpoint EF inClusters: FC01,FC02
Endpoint EF initialized: true
Endpoint EF manufacturer: unknown
Endpoint EF model: unknown
Endpoint EF profileId: C001
Endpoint EF stage: 4
A minute later, the Zigbee connection was lost, and I could not pair it again (C-8 Pro).
Shelly Gen4 are using the standard ZCL clusters for reporting the power and energy, so I suppose it will work with the inbuilt HE drivers, providing if it pairs and stays connected. I don't know why I can not pair it anymore, tried with all my HE hubs (C8 Pro, C8, C7 ), tried to use all my pairing workarounds - no success. Update: a link to a complex and tricky pairing sequence post on the Shelly forum.
Switching between Matter and Zigbee interface is working (5 quick presses of the device button), but starting the Zigbee pairing (3 quick presses) worked just once. I will try again after a few days.
The good news is that Shelly Gen4 Matter mode is working well! - Power, Voltage, Amperage, Frequency, and PowerFactor readings are correct and not spammy. There is a problem with the accumulated energy readings, however.
I have just updated the Matter Advanced Bridge .
