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":
I am inclined to agree with the sibling comment, so many uSD cards have just stopped working randomly on me in the past.
But, how are you plugging it in? I have some cards that just don't work with my uSD to USB adapter and instead I use uSD to SD and plug that into a hub I have.
They are so damn finnicky still though. I wish I knew better ways to test them.