EGroupware vs Proton Calendar

EGroupware has no write-up on Specifiction yet; its figures are above.

Proton Calendar is a calendar service for managing events, invitations, and recurring schedules on Android and iOS. Event titles, descriptions, locations, and invited people are protected with end-to-end or zero-knowledge encryption. A free Proton account costs nothing and allows up to 3 calendars. Paid Proton Mail plans allow up to 25 calendars, with calendar sharing by link to other calendar services on the web. Users can send invitations and add events from Proton Mail; appointment scheduling updates availability and adds confirmed meetings. The service supports scheduling links and video meetings, and notifications can arrive through desktop browsers or mobile devices. Calendar import and export are available on paid plans. Subscriptions purchased through proton.me renew automatically, and users can switch plans at any time; upgrades receive prorated credit. Proton is incorporated and headquartered in Switzerland and follows Swiss privacy laws.