Yubikey 5 is a popular commercial security key. We differ from them in the following:
1. Designed to be open, transparent design from the start.
2. Support signed firmware updates, that can be contributed to from community
3. USB-C and NFC
5. Lower cost
Yubico keys, in addition to supporting FIDO2/U2F, also support various OTP protocols and Open PGP. We are planning to add these same functions to Solo in the near future, and because of (2), you can securely update your token from our website when we are ready.