pin to ubuntu-22.04 as default runner OS

[samspills]

This week we saw a lot of chaos because the ubuntu-latest runner tag was switched to the ubuntu-24.04 image, away from the ubuntu-22.04 image¹.

I'm proposing that we pin the ubuntu runner OS to 22.04 as the default value so we can avoid that chaos in the future. By pinning we can

• test here before updating to a new runner tag, preventing CI for sbt-typelevel users from breaking unexpectedly (breaking due to this kind of change at least lol)
• communicate with users via a major release + release notes if a major change like this happens again

Footnotes

1. And that switch is now being rolled back for the time being 😵 ↩

[valencik]

Doing this would also save us an extra character width in the job names!
re: #761

[armanbilge]

👍 to pinning. Why go back to 22.04 / when should we go to 24.04 given that things are working now (I think 😅). I guess we can wait until GH makes 24.04 latest again, as a sign of stability? idk.

[samspills]

Why go back to 22.04 / when should we go to 24.04 given that things are working now (I think 😅). I guess we can wait until GH makes 24.04 latest again, as a sign of stability? idk.

I had the same thinking/question. I chose 22.04 so it would match the current behaviour of latest just in case, but it's not a strongly held opinion.
Edit: and then yeah, I agree with moving to 24.04 when the latest change rolls out again (hoping we actually get told it happens etc.)

[armanbilge]

Follow-up idea

• Constants for default OSes with pinned versions #764