Is there a safe method to drop the entire Akonadi database and resynchronize everything without losing the current configurations?
I wonder if an upgrade to newer postgres that we don't current properly support is causing all the problems with your upgrade. it really can't be akonadi itself. https://wiki.archlinux.org/title/KDE see section "4.4.1.2 PostgreSQL" might have some hints also there was some discussion related to akonadi+postgres17 at https://bugs.kde.org/show_bug.cgi?id=507899 that might trigger some ideas. beyond pointing you to some other web pages there's not much I can do to help as I know nothing about the backend databases.
I've been using PostgreSQL 18 for days and it worked flawlessly before the update. I'll take a look at your links right away.
My last attempt: Nuke Akonadi and reconfigure everything was also unsuccessful. The problems persist.