There's ongoing work to fight against this, it just takes a very long time because the problem domain is incredibly complex.

RISC-V [0] is an open ISA that looks promising. Unfortunately, the privileged instruction set is still a draft, which is important for getting a full modern OS up and running.

lowRISC [1] is as non-profit open hardware company that has been working on a fully open RISC-V-based SoC that can run Linux. In their about page they claim it'll be ready this year.

There's also the stuff from SiFive. They have an arduino-comparible microcontroller, and have ongoing work for a 64-bit quad-core. I don't think their hardware is open, though.

[0] https://en.wikipedia.org/wiki/RISC-V

[1] http://www.lowrisc.org