ArduPilot actions all getting stuck

We’ve been using github actions for the ArduPilot open source autopilot since September 2020. Generally has been very good, but over the last couple of days all our PRs are stuck for a very long time. Here is a typical one stuck for 11 hours:

How do we find out why we’re getting stuck?
Other PRs get through almost half the workflows, like this one which has done 28 and has another 28 queued.

Cheers, Tridge

A little more information - day-old pushes to PRs are getting this:

others are getting this:

Can't find any online and idle self-hosted or hosted runner in the current repository, account/organization that matches the required labels: 'ubuntu-20.04'
Waiting for a self-hosted or a hosted runner to pickup this job...

Switching to ubuntu-18.04 didn’t help.

Note this same problem is almost certainly being discussed over here: Hosted runners not picking up jobs - #5 by balupton

the problem has resolved itself