I have two FP3+ and this isn’t a new issue.
I have two different SIM in the UK (EE and O2) but when going to Settings > Network and Internet > SIM cards , although the SIM is tagged with the network the ‘Number’ has never been shown ‘Unknown’
I had this effect on my old FP2. For one of my SIMs it showed the number, for the other it didn’t. As far as I remember it was like that from the start and never changed with updates. My conclusion was that it was about the SIM card as the phone was clearly able to show something in some cases…
Can confirm that for a FP2. It’s the same on my one (number shown for one sim and for the other it isn’t). So I back the assumption it’s related to the sim.
Do you have any source for this specific claim? I cannot check it any more but I think in fact the SIM that showed the number in my case was the one that I had already migrated to a new operator - while the one that was “fresh” never showed it.
No no officiel source, just something mentioned and obsorved by several people in another Fairphone Group (includine myself). Still I can for sure not exclude there might also be other reasons