https://ninigiku.wordpress.com/2021/12/01/flashing-a-raspberry-pi-image-on-ubuntu/
The flashing of the SD card went ok, but applying the customizations fails with the error: Error creating firstrun.sh on FAT partition (Strangely it can write to the raw device, but it cannot read/write to the mounted filesystem).
The solution The solution luckily is really simple, but it is missed on a lot of forums. Snap installs can be configured using Ubuntu Software. The configuration allows a user to specify what kind of actions are allowed for the snap install. For the Raspberry Pi Imager we need to enable ‘Read/write files on removable storage devices’ as is shown in the image below:
Meine Lösung
Da ich kein Freund von snap bin:
$ sudo snap remove rpi-imager
$ sudo apt install rpi-imager