Excellent work @flohack!

That pointer to their developer documentation on Oxide is very useful! If anybody with connections back to Ubuntu can pass the word, the "Updating the Chromium version" text just has "TBD". For the long-term viability of UBports, it would be amazingly helpful if a Ubuntu wizard could fill in some details there!

just an update: my battery went empty and after I booted the phone the indicator was back again. (problem gone) Not sure what solved it, maybe the toggle of the rotation lock switch in system settings followed by a reboot...

There's an updated version of uNav in the Openstore. Upgrade to that and it should work - I hope. It works for me.