|T6459 KOrganizer: Invitations are not signed with GPG although signing is enabled by default
|T6520 KMail: invitations in decrypted messages not rendered
|T6521 IncidenceEditor: no way to show or change sign/encrypt state of iTIP message
Merged into master: https://invent.kde.org/pim/akonadi-calendar/-/merge_requests/59 and should be available in Release 23.08.
There's a fair amount of UI/UX improvements around the whole signing/encryption that could be done, for those directly related to this task I created new subtasks here.