docs: Add step to install working version on Ubuntu Pro - #14373

Description

The current install instructions do not work as expected with Ubuntu Pro at least on Ubuntu 24.04.4 LTS.

They appear to succeed, but are essentially a no-op: apt install gh behaves exactly the same as it would if the repo had never been added. The system installs a Ubuntu-maintained version of 2.45.0, and will never detect or install any newer version from the official GitHub repo.

This is because the gh package is present in the Ubuntu Enhanced Security Maintenance repo, and this has a higher pin priority than the GitHub repo.

This is exacerbated because 2.45.0 no longer actually works, due to later changes to the GitHub API.

Unless GitHub changes its packaging, the only workaround for this is for end-users to explicitly configure a preference for the GitHub repo.

How did you test this change?

• In the past, I had followed the official install instructions before first installing gh. I can see that I have the keyring, sources.list.d/github-cli.list etc with the expected content.
• I hit an error attempting to use gh this morning and identified that I was on v2.45.0
• I checked the repo and saw that the latest version is v2.100.0.
• I ran apt update - the first run (not in the screenshot below) failed due to the PGP rotation, but I fixed that without issues.
• I ran apt update && apt install gh assuming this would now upgrade me. The GH repo was fetched without warnings, but apt install gh reported that there was no newer version to install.
• I spent time googling / trying to find a solution. I found the advice / references below and added the preferences.d file as per this PR.
• I ran apt update && apt install gh and have now successfully updated to v2.100.0 (the latest stable at time of writing)

Key points

Notes for reviewers

This problem, and the solution, was identified by multiple separate users in:

• gh issue view fails with GraphQL deprecation warning for Projects (classic) #11992 (comment)
• gh issue view fails with GraphQL deprecation warning for Projects (classic) #11992 (comment)
• gh issue view fails with GraphQL deprecation warning for Projects (classic) #11992 (comment) - this includes a suggestion of adding this to the docs, but it was after the issue was closed and has not had a response.

It is also covered in
https://lukemanning.ie/blog/gh-issue-view-failing-ubuntu-deprecation-apt-pin

It may also be related to some of the cases reported in #9280 (although different posters in that issue appear to have different issues).

Authorship and follow-up

Who wrote this:

• A human wrote it.
• An agent wrote it under close human direction.
• An agent wrote it independently, and no human has guided the implementation beyond the initial prompt.

Who answers review comments:

• @acoulton will read and reply directly. Name the account.
• An agent will draft replies and @username will read them before they are posted.
• Nobody has explicitly committed to replying.