32blit
I came across an ad for the 32blit handheld game system on DistroWatch. Anyone know if it is 100% libre, including the bootloader? They say "all of 32blit's software, libraries, and firmware will be released under the MIT license", but I don't have the expertise to know if that allows for any escape hatches for unfree code to sneak in like a bootloader/BIOS or anything else.
They have a comments page where they are answering all questions, I think you could ask them directly: https://www.kickstarter.com/projects/pimoroni/32blit-retro-inspired-handheld-with-open-source-fi/comments