There are many physical wallets on the market for Bitcoin, but what if you could build your own ?
You can already do it by combining open-source software and RISC-V chips. This is possible with the M5 Stick V device. Or with the Maix Amigo. It is also possible to buy just the chip to put on your PCB.

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Do these projects use RISC V?
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No (although they all have software written Python, likely could work with RISC-V boards under Linux too).
My comment was answer to "what if you could build your own ?". It's possible already, without RISC-V, which is just a different CPU arch.
P.S. I plan to experiment with running Bitcoin node on RISC-V one day, so far haven't found any boards I like. Running nodes on different archs is more important than air gapped devices, where priorities should be security and cost, CPU arch is not so important.
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