After doing a couple of hours reverse engneering work, I am now 95% certain that this is connceted with a GOS update (prosumedly in June). That affected private spaces.
I'll cc Final (nprofile…yg8t)
I tested with three devices. The setup I was testing is InviziblePro + Monfluo & Cakewallet
LineageOS + InviziblePro - expected behaviour
GOS (without private spaces) + InviziblePro - expected behaviour
GOS (with) private spaces + InviziblePro in both spaces - worked with Cakewallet and Monfluo each in both spaces up to the GOS update in June.
Since the GOS update .onion connections stopped working.
Back then I spotted some Tor (onion) connectivity issues in Cakewallet, but since that had been a common issue in the past I was not expecting GOS (private spaces) to be the issue.
Up to the update both Invizible instances created their own ("independent") connection.
Now doing some traffic analysis it seems they are somehow tied to each other with a parent - child relation. Which should result in a "Tor over Tor" situation that then breaks down. This affects only native .onion connections. Clearnet-Tor over InviziblePro is not affected.
After deinstalling the Monfluo app from private spaces, the Monfluo app in the main space starts to work as expected again connecting perfectly fine to .onion nodes.
The same applies to Cakewallet.
I will try to close down the private space completly and reopen anew as there was a third app that had a corrupted database after the GOS update. I will report back if that solves the problem or if something needs to be done on GOS side to have private spaces work again as before.