Core Plot not drawing on macOS with old deployment version

We have an app that deploys to macOS 10.15, and if I use recent commits from the 2.4 branch, nothing appears on screen from Core Plot.

I traced this back to the commit: a4e0887

It seems there were changes made related to effectiveAppearance. I suspect the changes probably should be restricted to apps deploying to more recent versions of macOS.