I can confirm this.

I'm also curious if anyone in this topic has advice for how to make U2F a habit. I posted https://news.ycombinator.com/item?id=19316509, but didn't get anything. :(

I've found the Firefox U2F support on Windows, especially with Google, quite temperamental. It will prompt me to touch my Yubikey and I will, only to get some failure. I can't work out what causes it but replygging and retrying a few times normally gets me logged in. Very irritating.

No problem: I already registered it using Chrome on a different computer. Nonetheless, I consistently have trouble using it on Firefox on Linux.