docs(admin): rewrite maintenance and release schedule chapter

[joshtrichards]

☑️ Resolves

Rewrite the administrator manual's maintenance and release schedule chapter to make Nextcloud Server's release model, support lifecycle, and upgrade guidance clearer and easier to scan while making it about 30% shorter.

Changes:

• Add a concise TL;DR covering:
  • Version numbering
  • Latest versus oldest supported major versions
  • Release cadence and support duration
• Clarify the distinction between major and maintenance releases.
• Explain what administrators can expect from each supported major version.
• Improve guidance for choosing a version for a new installation.
• Clarify maintenance-release and end-of-life recommendations.
• Consolidate release-channel and major-upgrade guidance.
• Add guidance for beta and other pre-release testing.
• Document the independent release schedules of:
  • Nextcloud apps
  • Installation and deployment packages
  • Official clients
• Remove repetition and outdated or overly detailed wording from the previous chapter.

TODO

• Cover staged roll-outs?

🖼️ Screenshots

✅ Checklist

• I have built the documentation locally and reviewed the output
• Screenshots are included for visual changes
• I have not moved or renamed pages (or added a redirect if I did)
• I have run codespell or similar and addressed any spelling issues

[github-actions]

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📄 1 changed documentation page

• admin_manual/release_schedule.rst

Last updated: Wed, 05 Aug 2026 05:03:18 GMT