OK. I’ve thought long and hard about the decision here, and I am going to accept PEP 600. Congratulations to @njs for getting the proposal through to acceptance.
One reason I found this a difficult decision to make was that I remain concerned that the way the PEP specifies compatibility, in terms of a manylinux_tag_is_compatible_with_this_system function, does not match well in practice with how existing installers (i.e., pip and packaging.tags) currently handle compatibility. So I’d strongly recommend that implementing PEP 600 in packaging.tags be a high priority, in case it exposes any issues with the PEP.
Ultimately, though, the implementation plans are down to the manylinux developers, and I’m sure they will do a great job.