thunar displays "Ein Vorgang steht noch aus" for various USB-devices instaed mounting them

After plugging in an usb-device, this device shows up in /dev as sdb and sdb1. Tunar lists it as disk with partition "@" greyed out, ready to mount. Clicking on this greyed out disk thunar tells that a action is pending and does nothing. even after more than a quarter of an hour it is the same.
You'll wont get the device mounted.

Trying to mount manually as root shows same behavior: mount will do nothing over hours.

Unplugging, then replugging the device will create a new device. None of them can be removed.

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: thunar 4.16.6-0ubuntu1
ProcVersionSignature: Ubuntu 5.11.0-35.37-generic 5.11.22
Uname: Linux 5.11.0-35-generic x86_64
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Tue Sep 14 14:14:54 2021
InstallationDate: Installed on 2011-10-19 (3617 days ago)
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
SourcePackage: thunar
UpgradeStatus: Upgraded to hirsute on 2019-04-27 (870 days ago)