The software support for all other SBC's is universally terrible. They're Linux support is always questionable, incomplete, out of date, poorly documented etc etc.
If software matters then the only real choice is Raspberry Pi.
There are good ones. They just cost real money. Which is the issue.
What do you mean by that? Isn't the Pine64 stuff supported by mainline Linux?
Much of it is mainline, yes. So I’m thinking they expect x86 like compatibly.