Here's the thing about SMS: your great aunt who doesn't know what a JPEG is, knows what a text is. Ok, she might not fully "get it" but she knows where to find a text message in her phone. My tech-literate fiancée struggles to get her YubiKey to work with her phone, and I've tried it with no more luck than she's had. YubiKeys should be supported but they're miles away from being usable enough to totally supplant other 2FA flows.
Here's the thing about SMS: your great aunt who doesn't know what a JPEG is, knows what a text is. Ok, she might not fully "get it" but she knows where to find a text message in her phone. My tech-literate fiancée struggles to get her YubiKey to work with her phone, and I've tried it with no more luck than she's had. YubiKeys should be supported but they're miles away from being usable enough to totally supplant other 2FA flows.