It's not at all straightforward, it should be the kind of thing that's just a compiler flag, as opposed to needing to restructure your build process to support it.

Yeah that's what I meant. I also came across some script with redefinitions of C standard library functions that supposedly also allows you to link against older glibc symbols. I couldn't make it work.

Any half-decent SDK should allow you to trivially target an older platform version, but apparently doing trivial-seeming things without suffering is not The Linux Way™.

The reason that there is no SDK is because containers (and before that sysroots) are good enough that no one bothers to maintain the 100% usability solution.

It's not straightforward and yes it should be easier, but it's also not rocket science. Containers have made it approachable for the average developer.