I'm on Linux. I have an SD card which has been giving me a number of strange problems for a while now. It now appears to have wiped itself completely. Looking in GNOME disks the main partition, which I expect to be exfat, is of type "unknown". If I run fsck.exfat, It claims it's not a valid exfat image.

Windows refuses to even look at it.

Before I destructively image the disk, do you think there is ANYTHING else I can/should try to see if the data is still easily recoverable?

$ sudo /sbin/fsck.exfat /dev/sdb1
[sudo] password for mcc: 
exfatprogs version : 1.2.9
Bad fs_name in boot sector, which does not describe a valid exfat filesystem
ALT

Replying to @⁨mcc@mastodon.social⁩

@mcc@mastodon.social

The suggestion at the end of this might be a viable option.

Use application, 'testdisk' to analyze without writing any changes. If it can detect the lost exfat tables then it can be recovered. I have done this with multiple failed media and drives. Be sure to read the documentation carefully before running it.

Exfat writes a backup boot region. Testdisk should be able to check for this.

If that doesn't work there is ddrescue and photorec for finding and recovering individual files.

You might also use 'dd' to raw copy the damaged volume to an image file and write that image file to other external media then try running 'testdisk' and other tools on the copy. You can keep the image file as a backup as you try to recover the data from a copy first, to avoid the risk of further damage to the card.