The Xous distro that the Passport Prime uses has the right idea from a design standpoint. Microkernel, memory safe languages used throughout, mandatory sandboxing for apps. Xous is mostly designed for embedded systems. Obviously implementation is a different thing to rate compared to just the design. I also haven't looked into the hardware as much. I would take it as one of the better offerings the HWW market has right now. Secureblue has a server distro, hardened CoreOS. I would assume a lot of these bitcoin one-click server dashboard distros aren't as hardened to such an extent. Perhaps it's a room for improvement for these projects. A lot of defence corps sell their own OSes with the above as marketing, 'STOP OS' by BAE Systems comes to mind. Good luck being able to copy of it yourself though.