Backing up

Laptop

• Sync to Nextcloud.
• Everything else is ephemeral (i.e. can be lost, or is already stored in Git somewhere).

Web server

• MediaWiki: dump SQL, pages XML, and copy /images.

Mobile phone

• SMSs from Android: SMS Backup +, to IMAP.
• Annually export chat logs from WhatsApp to Nextcloud, and then clear from phone.
• Keep no photos, GPXs, etc. on phone.

Other

• Emails: nopriv, email-archiver. Thunderbird 'archive' feature, moving things to Local Folders which are stored in Nextcloud.