Public CalDaV Calendar and Thunderbird

is it possible to create a public Calendar that can be embedded with CalDav in for example Thunderbird or OpenSync for Android without authentification and read only access? Also is it possible to restrict the access to the calendar app to specific users or user groups?

it seems like thunderbird currently has general trouble with cal and carddav and nextcloud but owncloud is working fine?

Access to the calendar app can be restricted to a user group. Check-out the Apps configuration.