There seem to be some invalid plasmoids? Or an unfinished update? The error messages like "PlasmaCore.IconItem is not a type" look like a Plasma5 version of some plasmoid as that should by now be "Kirigami.Icon" (see https://develop.kde.org/docs/plasma/widget/porting_kf6/ )
I'm not sure which plasmoid is actually giving the error message, so it might be a third-party one, that's to blame?
~Naturally you must not use the store~
"You must not" equals "you are not allowed to". I think you meant "you don't have to".
Sorry to nitpick, and thanks for all the work you and all KDE contributors are doing.