1. Ubuntu 21.10 is not supported with plugins. 22.04 is the latest LTS, and is
supported, at least for o-charts_pi.
2. I am not sure that OCPN native on 22.04 will handle 1024x600 screen
any better than flatpak. This screen config was evidently not well tested. Have you tried OCPN on Ubuntu 22.04 ?
3. We can "fix" the o-charts license
reset once we figure out what system you should be using on this device. Don't worry about that just now, please.