I am not sure upgrade problems can be avoided in general.
A way to mitigate upgrade problems could be:
- by default freedombox are not migrated automatically to a new stable Debian version
- the migration is only attempted by users with some experience and willingness to deal with problems
- these users report problems, try finding solutions, document them and write sufficient (and reasonably easy) guidance to fix all the detected problems
- when that is ready, users are invited to check the guidance and upgrade
Some coordination may be useful, this forum is already a nice tool to share problems and solutions. If we want to do more than, that requires volunteers and and some kind of organization.
I am not sure how long would be needed until upgrade by everyone, perhaps one or two months?