After upgrade to TW 20210731, the mount applet of KDE/Plasma ignores my card
reader after I have mounted and safely removed it once.

I.e., after boot, when I insert an SD card the removable devices dialog pops up
and allows me to mount the card.  As soon as I 'Safely Remove' it after use,
the card reader becomes invisible to the applet.

It is not listed in the volumes of the applet, so I cannot use it to mount a
card inserted there (I don't automount, only on manual request).

If I open the settings dialog, an inserted card is listed there, also
/proc/partitions does show it:

 179        0    7761920 mmcblk0
 179        1    7757824 mmcblk0p1

and I can manually (from terminal) mount the card.  Just not from the applet
anymore.

It looks a bit similar to the (IMO brain-dead) behavior to completely remove
USB devices from the system when umounting it - one has to dis- and reconnect
the device to make it visible again.

The card reader, however, is built in fix in my laptop.  No way to disconnect
it.  Only removing and re-inserting the SD-card (or even a different one)
doesn't help.