I got it working and one should follow the documentation There it says:
Zigbee
To use Zigbee with ZHA configure the Integration as follows:
Remember/copy the hostname of the add-on (e.g. c8f00288-silabs-multiprotocol).
Add the Zigbee Home Automation (ZHA) integration to Home Assistant Core
When asked for the Serial Device Path, choose Enter Manually. 4. Choose EZSP as Radio type. 5. As serial path, enter socket://<hostname-from-above>:9999. 6. Port speed and flow control don’t matter.
Press Submit. Adding ZHA should succeed and you should be able to use ZHA as if using any other supported radio type.
I am assuming you did not have ZHA before installed? for those of us attempting to migrate from Sonoff or similar that already has the ZHA configuration installed, we cannot add it again. I am unclear what the migration path is for us in such a case.