I’ve finally had an update from FP Support (other than factory reset) on the case I raised:
We have recently become aware of a software issue which makes it impossible to use most SD cards. Our developers have found the root cause of the issue and a fix will be available via a software update in the near future.
I can not give you a specific release date yet, but it should be before the end of February.
The path to a fairer electronics industry has its fair share of obstacles, and we appreciate your continued support and patience while we work on this matter.
I will put this ticket on hold for now and let you know once the software update is released.