Most vendors of non-free software do support macOS (or viable alternatives are available). I strongly doubt many of them will even come to Linux. Because it requires more standard configurations. Apple had to make its main FS case insensitive before vendors like MS and Adobe were porting their software.

I like having my own choice in configuring my system. That amd freedom is why I use Linux desktop.

But yeah, the main justification for an open-source power-user desktop OS is a backup plan in case macOS dies, which isn't a very good business case.

This is a yuuuge generalization. There are many Linux folks who want a slick consumer experience and there are many that want ratpoison and vim. :-)

This idea doesn't take away from the requirements that people have for a non-consumer desktop.