Document unsupported reason 'home_assistant_core_version'

[agners]

Proposed change

Document when we declare an installation as unsupported due to outdated Home Assistant Core version.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logos and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Added documentation for a new feature I'm adding to Supervisor (current branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: Check Core version and raise unsupported if older than 2 years supervisor#6148
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

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[Copilot]

Pull Request Overview

This PR adds documentation explaining why Home Assistant installations become marked as unsupported when running outdated Core versions. The documentation explains the 24-month support policy and provides guidance for updating safely.

• Documents the 24-month (approximately 24 releases) support policy for Home Assistant Core versions
• Explains the impact of running unsupported versions (no updates for Core or add-ons)
• Provides step-by-step guidance for safely updating outdated installations

[home-assistant]

It seems that this PR is targeted against an incorrect branch since it has a parent PR on one of our codebases. Documentation that needs to be updated for an upcoming release should target the next branch. Please change the target branch of this PR to next and rebase if needed.

[sairon]

LGTM with minor remark, but maybe it's not necessary to delve into the details.

[c0ffeeca7]

Home Assistant Core version is a very generic title. Can we add the symptom in the title? Or is there a reason to just mention that it's something about the Core version?

This page seems like a troubleshooter to me.
We could use the Symptom, Description (or Cause), Resolution structure here.

[agners]

These more-info unsupported come all in the same format, e.g.

https://www.home-assistant.io/more-info/unsupported/network_manager
https://www.home-assistant.io/more-info/unsupported/os_version

In a way the breadcrums above say that its about unsupported, but maybe that is not really clear enough. I think if we want to change then we should all at once, e.g. prefix with Unsupported: ... Or Unsupported - ...

[c0ffeeca7]

tweaks

[home-assistant]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

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[c0ffeeca7]

Thank you, @agners and @sairon 👍