Linux: SD card "error -84 requesting status"

[^rooker]

Inserted an SD card into a notebook (Xubuntu 20.04.3) and nothing happened: Nothing showed up for mounting.

"dmesg" shows the following error message:

[41117.523403] blk_update_request: I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[41117.523405] Buffer I/O error on dev mmcblk0, logical block 0, async page read
[41117.523442] ldm_validate_partition_table(): Disk read failed.
[41117.607338] sdhci-pci 0000:00:14.5: error -84 requesting status
[41117.607340] mmcblk0: recovery failed!
[41117.607344] blk_update_request: I/O error, dev mmcblk0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[41117.607346] Buffer I/O error on dev mmcblk0, logical block 0, async page read
[41117.653715] mmcblk0: unable to read partition table

Tried to web-search it, but got *no* results for "error -84"
That's odd.
Getting an error message that noone else had so far is usually not a good sign.

It's either such a weird coincidence that caused it, or something very bad. Or something else.

To be continued...