OpenMarine

I have a laptop where I installed RaspberryPi OS as a clean install. I have followed the instructions to install Openplotter (installed settings 3.6.6 etc). Using OpenCPN Installer 3.3.0 fails to install OpenCPN. After "Checking versions" the respond is:
Debian/Ubuntu. Recommended for LTS-system.....
Installed: none
Candidates:
Debian/Ubuntu:

Going back to "Install" tab/icon, everyting is dimmed.

The terminal show:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/openplotterOpencpnInstaller/openplotterOpencpnInstaller.py", line 193, in OnToolCheck
    self.logger.WriteText(+' OpenCPN '+str(self.table['debian']))
TypeError: bad operand type for unary +: 'str'

What am I doing wrong?