However, I do think that Boost could benefit from more diverse test runners than what GitHub Actions offer (more hardware architectures, more OSes, more compilers). I'm also concerned about depending solely on GitHub Actions for testing, since this is a single point of failure that historically does tend to fail from time to time and is difficult to replace.
Drone in the boostorg has native s390x and aarch64. I would prefer if the current test matrix evolved into
something more useful, an alternative to GHA, but I realize this is probably a lot of work. If not that, I think the resources could be better spent on improving GHA quality, e.g. as new GHA runners.
BTW, on the topic of improving GHA quality, there is this collection of GHA plugins that run the CI on various OSes in VMs:
There's also: https://github.com/jeking3/bdde which plugs right into boost.ci. I use it for testing ppc64le since the cost of testing on a native machine was astronomical. Matt