The above is all about getting the build system to work at all. If that isn't a showstopper there's a subsequent discussion to be had about older platforms where one could get the build system to work but convenient packages are missing. For example not even RHEL7 has any Python3 packages in the base system (it does in Software Collections though) which means some extra hoops on getting meson running there. And RHEL5 is in an even worse spot as it has no Software Collections, who knows if Python 3 builds on it out of the box etc.
I would expect that a new version of software should not target versions of platform that are end of full support. Per https://access.redhat.com/support/policy/updates/errata currently only RHEL7 is at Full Support, and RHEL5 is already past Product Retirement. I would say it's fine to support these at already released branches, but limiting .
