I've got a backported linux patch to support pinebook pro with
linux-libre 5.4.x. It's very limited support... no LCD, no battery
status, no RTC, etc. but it works!

The one reason I haven't pushed the patch is it would cause useless
rebuilds of linux-libre for x86_64, i686 and armhf; I've been trying to
make that conditional for aarch64 and not been very successful at it; if
someone could help with that, or give me the go-ahead to merge as is
... that'd be great!

live well,
  vagrant