[gf000]

Show me any device on earth that can run a browser that has no proprietary code whatsoever (including hardware) on it?

[SXX]

AFAIK older Talos Secure Workstation with Power CPUs was it. Everything open including CPU firmware.

Not sure about smartphones though - they mostly struggle with a fact there are no truly open source baseband.

[Andromxda]

There is no smartphone fully powered by open firmware. Also keep in mind that the hardware itself is proprietary too.