qFlipper can't connect to device on Ubuntu

I keep getting an error message on qFlipper stating [RPC] Starting RPC session…
[RPC] Failed to start RPC session: Failed to begin CLI session: Device is not responding. I know it has nothing to do with the device as it works with windows. I updated the firmware via bluetooth. Prior to the firmware update I still had the same error message. It says permission denied, cannot connect to serial port as well. I have tried searching google and tried it all. Nothing has solved the solution

Had the same issue on Fedora.
Make sure your user is added to dialout group sudo usermod -a -G dialout $USER .

Try to start qFlipper from console and see the port is used, looks like
[DBG] Trying serial port at /dev/tty*

If it detects as anything different then ttyAMC then you need to add udev rules.
Run qFlipper from terminal with parameters ./qFlipper* rules install.
This will prompt you for sudo and then try lunching qFlipper.