I found it out by my self.
Take the CalDAV adress which Synology recommends for Thunderbird (not macOS / iOS):
Synolgoy Calendar:
Put the the server address, user and password in the dialog above (Ubuntu touch: Settings -> Accounts)
I found it out by my self.
Take the CalDAV adress which Synology recommends for Thunderbird (not macOS / iOS):
Synolgoy Calendar:
Put the the server address, user and password in the dialog above (Ubuntu touch: Settings -> Accounts)