Tested on my Dogwood phone, with Nextcloud set up in Gnome Online Accounts:
Seems to work, have not checked full functionality
Works so-so. It seems the Gnome Contacts app uses some different fields from the Nextcloud Contacts app…
Also, Gnome Contacts often crashes when updating a contact.
Can’t tell. I installed the Nextcloud app from PureOS repo, but it doesn’t scale well to the small screen.
Also, seems it doesn’t use the Nextcloud account I have set up in Online Accounts.
As an aside, entering the Nextcloud app password in Online Accounts is painful, but I assume this will improve when cameras are working and there is a QR scanning app.