Calendar invitation / deletion behaviour


I’m testing Nextcloud as an alternative to Google Workspace.

Invitations sent to externals (like a Gmail user) can’t be accepted or declined (that is: only with the in-mail buttons, but not with the buttons most mail clients put over calendar invitations), and when you accept or decline invitations sent by externals (like a Gmail user) your status in their event doesn’t get updated either.
When they delete the event you got invited to, it’s also not deleted from the Nextcloud calendar automatically. for example handles this like it should be handled. (Tested with a personal Gmail account and trial account, and that trial account is also used for Nextcloud mail)

Is this behaviour as expected? Or is there something wrong with my installation?

I’d also like to use a better mail client like Roundcube (mainly need a more featured mail editor, but also need schedule sent which Roundcube Plus has a plugin for), but am afraid this will be even worse with it’s integration with the calender. Can anyone comment on this?