Thanks Simon for bringing this up! Our first need is to have someone volunteering for maintaining our current test infrastructure - Christian is helping with this right now but cannot afford to become the maintainer right now.
Philip, is this something you would consider? If so, that'd be very helpful. Let me know your SourceHut username and I'll give you access to https://git.sr.ht/~bzg/org-mode-tests/ I am a paid user on SourceHut and I'm happy pulling org-mode-tests from the orgmode.org server to build from the latest repo manifests. Once we solve this maintenance issue, we might consider evolving the tests so that they use Guix instead of Debian if it provides a real benefit for our needs. In the meantime, this test infrastructure has already proven very useful IMHO. Thanks, -- Bastien