My SD card that had been not working since the FP5.UT2B.B.072.20240920 update is now working again! I have always been too lazy to re-format it, but I’m happy it’s back.
This confirms my suspicion that it was a software problem.
This is the exact message where I reported that it was broken after the update: Software Update: FP5.UT2B.B.072.20240920 - #21 by RubenNL