I tend to get the U2F-only Yubikeys (a.k.a "Yubico Security Key", they are blue instead of black) because I don't want to inadvertently start relying on Yubico

I tend to get the U2F-only Yubikeys (a.k.a "Yubico Security Key", they are blue instead of black) because I don't want to inadvertently start relying on Yubico proprietary functionality, and they are cheaper. This is just one more reason to do so.