Try logging in as a different user. I plugged in 2 sticks at once on TW20211213. Three of four partitions showed in Plasma’s popup, and as selected, each of the three mounted:
# dmesg tail
136.663747] ext4 filesystem being remounted at /run/systemd/unit-ouser/var/tmp supports timestamps until 2038 (0x7fffffff)
401.948901] usb 7-3: new high-speed USB device number 3 using ehci-pci
402.234865] usb 7-3: New USB device found, idVendor=13fe, idProduct=4300, bcdDevice= 1.00
402.234874] usb 7-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
402.234878] usb 7-3: Product: USB DISK 2.0
402.234880] usb 7-3: Manufacturer:
402.234883] usb 7-3: SerialNumber: 90000983E198BB33
402.275491] usb-storage 7-3:1.0: USB Mass Storage device detected
402.275728] scsi host8: usb-storage 7-3:1.0
402.275861] usbcore: registered new interface driver usb-storage
402.280931] usbcore: registered new interface driver uas
405.267540] scsi 8:0:0:0: Direct-Access USB DISK 2.0 PMAP PQ: 0 ANSI: 4
405.268028] sd 8:0:0:0: Attached scsi generic sg2 type 0
405.271377] sd 8:0:0:0: [sdb] 15132672 512-byte logical blocks: (7.75 GB/7.22 GiB)
405.274211] sd 8:0:0:0: [sdb] Write Protect is off
405.274217] sd 8:0:0:0: [sdb] Mode Sense: 23 00 00 00
405.276002] sd 8:0:0:0: [sdb] No Caching mode page found
405.276006] sd 8:0:0:0: [sdb] Assuming drive cache: write through
405.295021] sdb: sdb1 sdb2 sdb3
405.300026] sd 8:0:0:0: [sdb] Attached SCSI removable disk
410.024953] usb 7-4: new high-speed USB device number 4 using ehci-pci
410.182121] usb 7-4: New USB device found, idVendor=0781, idProduct=5581, bcdDevice= 1.00
410.182130] usb 7-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
410.182133] usb 7-4: Product: Ultra
410.182136] usb 7-4: Manufacturer: SanDisk
410.182138] usb 7-4: SerialNumber: 4C530000210529123153
410.183191] usb-storage 7-4:1.0: USB Mass Storage device detected
410.184234] scsi host9: usb-storage 7-4:1.0
411.209903] scsi 9:0:0:0: Direct-Access SanDisk Ultra 1.00 PQ: 0 ANSI: 6
411.210261] scsi 9:0:0:0: Attached scsi generic sg3 type 0
411.211509] sd 9:0:0:0: [sdc] 120127488 512-byte logical blocks: (61.5 GB/57.3 GiB)
411.212761] sd 9:0:0:0: [sdc] Write Protect is off
411.212766] sd 9:0:0:0: [sdc] Mode Sense: 43 00 00 00
411.216274] sd 9:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
411.253169] sdc: sdc1
411.257142] sd 9:0:0:0: [sdc] Attached SCSI removable disk
487.864495] FAT-fs (sdc1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
490.458721] EXT4-fs (sdb3): mounting ext2 file system using the ext4 subsystem
491.538937] EXT4-fs (sdb3): mounted filesystem without journal. Opts: errors=remount-ro. Quota mode: none.
494.897308] ISO 9660 Extensions: Microsoft Joliet Level 3
494.905065] ISO 9660 Extensions: Microsoft Joliet Level 3
494.909850] ISO 9660 Extensions: RRIP_1991A
# df -h | egrep -v 'sda|srv'
Filesystem Size Used Avail Use% Mounted on
/dev/sdc1 58G 1.2G 57G 2% /run/media/ouser/DFSPUP64BIO
/dev/sdb3 3.4G 32M 3.3G 1% /run/media/ouser/usrlclusb
/dev/sdb2 3.9G 3.9G 0 100% /run/media/ouser/openSUSE-Leap-15.4-DVD-x86_64119
I don’t know why the openSUSE 15.4 ESP on sdb1 didn’t show in Plasma’s popup.
I don’t know much else to suggest, except to wait for the next complete KDE rebuild (last happened around 3 days ago IIRC), and if it still is a problem after that, report a bug.
If you have BTRFS and snapshots, roll back 3-4 days or more to see if it still happens there.
Another thing: any time Plasma does strange things that you can’t stop, log out of it and delete ~/.cache/* before logging back into it.