Oh, there are now #FIDO security keys based on #Google's #OpenSK firmware for #Titan based on #TockOS (both in #Rust), available for purchase:
https://shop.ftsafe.us/products/opensk-v2
Do note that these do *not* feature a secure element and are not resistant to more advanced physical attacks or side channels, although still probably an upgrade to disk storage as long as you keep the key safe:
https://feitiantech.github.io/OpenSK_USB/caution/
Nevertheless, an interesting toy!