Summary

The ubuntu-20.04 GitHub Actions runner image, currently used in the tests.yml workflow will soon be unsupported, as notified at: actions/runner-images#11101

Proposed fix

Ubuntu 20.04 itself is a long-term-support release, however it is also nearing the end of that support cycle, and will no longer be supported by Canonical from May 2025: https://ubuntu.com/20-04

I'd suggest removing the ubuntu-20.04 jobs from the tests.yml workflows at the end of this month (March 2025).