Formatting a "corrupt SD card" fails - is the card dead? I have a no-brand-marked 32 GB "Micro SD HC" Card, which I'd been using with my Android 6.0.1-based phone.

Recently, the phone has been telling me the card is corrupt, and would not use it; and today I tried formatting it as the UI suggested. Well, the formatting app closed after a very long time with no progress beyond some point, and nothing seems to have changed - the card is still described as corrupt.

Is it necessarily the case that my card is dead, or could this possibly be a software issue?
Most likely. If you had the card set to be read as internal storage, Android sets an encryption on it. After a factory reset, the keys change, and the card is permanently write-protected. I have had no luck reversing this on mine.

Regards.