After several test I think the problem come from the identity of the event organizer that is not correctly transmited when creating an event from some Android calendar apps. Nextcloud calendar server is then not able to match with the Nextcloud user that organize the event and thus doesn’t send invite emails. By using Samsung Calendar and using my NextCloud user email address as my DAVx5 account name, I have been able to solve the problem.
If I create an event from NextCloud webapp and Invite one email :
One organizer : the identity of my Nextcloud user account
Invitation email is sent
If I create a new event from SimpleCalendarApp, synchronized with DAVx5, I inivite one email. The event created in nextcloud :
No invitation email
If I do the same operation from Samsung Calendar app :
This time there is an organizer. The organizer name value is the DAVx5 account name I choose during DAVx5 configuration.
No invitation email is sent
I try to rename my DAVx5 account to match my NextCloud account, but It still not match with my NextCloud account (note the missing profile pictue) :
I finally found a solution!
The match between the organizer identity on Android and the NextCloud user is based on the NextCloud user email address. So I rename my DAVx account to match the email of mu NextCloud user (in the profile page), then the NextCloud calendar server is able to find my account and send invitation mail to attendees.
Do not display Nextcloud profile icon
But invitation mail is correctly sent to attendees