general

• calendar & contacts sync/sharing (caldav) → https://docs.nextcloud.com/server/13/user_manual/pim/index.html
• filesharing → https://nextcloud.com/files/
• webmail (imap client)
• notes (sync between desktop/mobile/web)
• video conf & chat → https://apps.nextcloud.com/apps/spreed and/or “Nextcloud Talk” ios/android app
• federation (w. other nextclouds)

specific

• “find my iphone” (AAPL) → https://apps.nextcloud.com/apps/phonetrack
• polls (e.g doodle, loomio, etc) → https://apps.nextcloud.com/apps/polls

• https://docs.nextcloud.com/server/16/admin_manual/index.html
• apache2, php-fpm, postgresql

etc

• etc+