This is very smart, can you tell me how you setup the USB that it can only be opened in Linux OS? I think this will be very useful for me because many people don't like using Linux OS, for example, in my country you will never see anyone running Linux on their PC, it is always Windows OS.
I don't know if will come across this reply, if you do pls drop a message or PM about how you make this work.
Linux can open any USB. Although, if you want an encrypted one, you can get hardware encrypted USBs which I'd much prefer than doing it via software, but you've ultimately got to trust the manufacturer of the device, since they've implemented the security, and more often than not they're closed source. You basically setup a pin number on the hardware, and then you put that pin in, plug it in, and it's unlocked. You can make them read only too, which is quite good for operating systems, and when you want to install them or plug in a live usb to a potentially infected computer, and take a look around.
I've got a few hardware encrypted one's, but I probably wouldn't trust them enough to put my seed onto them. I much prefer physical backups.