Like SoloKeys? The Solo 2 has a firmware written in Rust: https://solokeys.com
And the documentation, at least when I received the keys, felt incomplete and hard to find; it did not give me confidence in the product.
I still use them as a backup key, but I decided to just by two yubikeys as my main keys.
With that said, I had a Yubikey Neo die for me as well (NFC still worked, USB totally dead) - Yubikey offered me a new key for a discount.