My choice would be a coldcard with the seed generated by dice rolls. I wont say seedsigner is a bad option because I have one and its an awesome project but just be aware that the rasp pi is a general purpose computer with a bigger attack surface than a piece of hardware specifically designed for storing private keys like the coldcard. If you want to build your own, this is a project with more hardware options to build on that are better (in my opinion) and cheaper than a rasp pi. https://selfcustody.github.io/krux/. But again the attack surface is still bigger when you use hardware that is not specifically designed to store private keys.