Ultimaker 4.8.0 on Linux can not use /dev/ttyACM0 device; permission denied

[rverh 0]

I am a new user of Ultimaker 4.8.0 on Linux.

I run Ubuntu 18.04 and downloaded the Appimage Ulitmaker_Cura.

 

The printer is a XYZ printer with USB connected.

 

The Ultimaker software can not connect to the printer.

The log entries:

2021-03-05 10:40:40,403 - DEBUG - [Thread-2] USBPrinting.AutoDetectBaudJob.run [50]: Checking /dev/ttyACM0 if baud rate 115200 works. Retry nr: 1. Wait timeout: 15
2021-03-05 10:40:40,407 - WARNING - [Thread-2] UM.Logger.logException [106]: Exception: Unable to create serial
2021-03-05 10:40:40,410 - WARNING - [Thread-2] UM.Logger.logException [110]: Traceback (most recent call last):
2021-03-05 10:40:40,412 - WARNING - [Thread-2] UM.Logger.logException [110]:   File "/build/env/4.8/inst/lib/python3.5/site-packages/serial/serialposix.py", line 265, in open
2021-03-05 10:40:40,415 - WARNING - [Thread-2] UM.Logger.logException [110]: PermissionError: [Errno 13] Permission denied: '/dev/ttyACM0'
2021-03-05 10:40:40,418 - WARNING - [Thread-2] UM.Logger.logException [110]:
2021-03-05 10:40:40,420 - WARNING - [Thread-2] UM.Logger.logException [110]: During handling of the above exception, another exception occurred:
2021-03-05 10:40:40,423 - WARNING - [Thread-2] UM.Logger.logException [110]:

 

etc. etc.

 

I have tried to run the package with sudo, but that doesn't wok either.

 

Does my useraccount need to be a member of a special group?
Or is there anyone else that can shed a light on this?