How to get it working with UniFi-CloudKey-Gen2-Plus?

How to get it working with UniFi-CloudKey-Gen2-Plus? I can see from the review on February 5, 2021, that the user darco was able to get it working with Gen2 CloudKey. But unfortunately darco didn’t specify, how he got it working…

What I do know is that Gen2 is not using port 8443 anymore, but access is done straight to HTTPS/443 port.

And I’m able to query the device info from the browser from:
https://[local-IP-of-Gen2-CloudKey]/proxy/network/api/s/default/stat/device