A more (or less?) funny is the fact, that the current radxa ubuntu images really don’t boot out-of-the-box. In the other thread I have described the issue, so I put the link here for people looking for the problem. (Radxa does not look like to have noticed anything and fix it.)
An additional issue is the fact, that the boot partition is not marked as msdos/FAT type, so that other systems have problems to automount it and it must be (force)mounted manually in order to fix the problem.