On my Fedora44 system I installed flatpak OpenCPN.
Installation was smoothly. I can launch OpenCPN and install charts. But not charts from o-charts. O-charts sell online charts, cheap an very well maintained. O-charts is integrated in OpenCPN. You need the o-charts-plugin to install and display the charts. For Fedora you also need a usb-dongle. This is clearly described in the OpenCPN manual.
Sadly I could not download the charts from o-charts despite the installed plugin and the dongle. It turned out that one has to add a rule to /etc/udev/rules.d.
This not mentioned in the OpenCPN manual.
Why is this udev-rule not included in the flatpak OpenCPN package?
Short answer:
The udev rule would need to be added to the system in order to work.
However, a Flatpak is run inside a sandbox, separating it from the system. Access to the system is only possible with specific permissions.
Changing a udev rule in the system folder /etc/udev/rules.d is not possible for a Flatpak, at least not in an straightforward way as it would be for an unsandboxed application.
This is better for security, but can limit certain actions.
The Flatpak distribution of OpenCDN is not supported by the developers themselves, but a third-party, which is why this is not mentioned in the manual.
You could talk to them if adding a note about that in the manual could be done though.
That is a very clear anwer.
Thanks.