Excellent AddOn and must have for Nextcloud, Zentyal and SOgo. Could be five stars but looses color in calenders in the windows version on Zentyal's SoGo - all calendars are grey (color choosen in Linux is kept with Nextcloud). Update: Unfortunately one can not change the color of Zentyal SOGo. If you connect the calendar natively using lightning you can overwrite the color from TB side.
This review is for a previous version of the add-on (0.7.18).