I'm trying to read a (probably damaged) microSD card from my computer (tried with two different computers, both Arch Linux, which can read other card without any problems).
There isn't any singal of life (no /dev/sdX, nothing with GParted, testdisk, ...); the only thing that I found was in dmesg.
Here's the output of sudo dmesg | rg "mmc0":
mmc0: cannot verify signal voltage switch suggests something is wrong with the hardware (either SD card or card reader). -110 is a timeout error, and -123 generally indicates a problem with media hardware.
You're not gonna fix this with software. Try a different card reader, or if you think it's the SD card, put a bit of alcohol on a cotton swab and gently clean the contacts. Let the card fully dry, then try again.
Obviously this is a hail-merry shot, but your card is likely physically done for
If you need the data, a solid state recovery specialist may be able to assist you. Surely won't be cheap as it generally requires reading directly from the flash through soldered wires or jigs.
Try putting it in the freezer for a few minutes before trying to read the data. Or heat it up slightly.
This is an old trick I've used to recover data from a hard drive or two. I suppose it could help if the problem with the SD is some kind of microscopic fractures.
It should be emphasized that this is just a temporary workaround at best.
If you just want to try to recover, PhotoRec
This does require it to at least be able to power and have a raw device to look at, though it doesn't have to be able to be mounted. More than just photos can be recovered.
Had pretty close to the same results with PhotoRec vs commercial tools on windows.
Just for clarification, were you able to read the card from this machine before?
I had a similar issue where my SD card reader was not able to read a card with a newer standard like SDXC or whatever it was and i had to find a newer reader.