When do you expect to release 2.2.0 to have the feature in production?
Sorry, no date yet. I hope we will see some progress on the automatic build pipeline, which will reduce the effort of building new releases tremendously, so that we can increase the frequency.
That’s a good point - for openhabian with NGINX as a reverse proxy on port 80, no change should be needed (as long as you do not configure any authentication, which is actually one of the main purposes of NGINX here 
).
when I try to start the devicescan from google assistant on my pixel
it looks like this
So does it actually work or does it run in a timeout?
Is it a difference to use Assistant vs. Home?
There might be - you are redirected to account.meethue.com, which looks as if this tries to do a Cloud-Integration. In my video you might see that the redirect goes to hue-adapter.appspot.com, which is not hosted by Philips, but probably just holds the code to do local discovery through UPnP.