The last (scheduled) release of Plasma 6.0 is here, with another round of bugfixes. Next up: The Plasma 6.1 series, initial version will be released on June 18th (if everything is going to plan).
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?
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?