I don't have 2FA enabled on my eBay account. I use a unique, complicated password though, and I don't see any suspicious activity on my account, though, apparently eBay saw something wrong. Unfortunately they won't tell me what's wrong, so I can't figure it out or help.
AFAIK eBay doesn't support WebAuthn. I got a set of 3 Yubikeys some months ago (1 for my laptop, 1 for my workstation, 1 for backup in my fire safe) and I wanted to protect my eBay account using them, but eBay only offers me options to add SMS or eBay's mobile app as 2nd factors.
They do support WebAuthn, but only on Windows. (It works perfectly fine on Linux if you spoof your user agent.)
Also note that the option is not under "2 step verification" but a separate "Security key sign in" section lower down, because their implementation is not really 2FA, it's just an additional login method (email + security key) and it doesn't disable regular email + password login.
AFAIK eBay doesn't support WebAuthn. I got a set of 3 Yubikeys some months ago (1 for my laptop, 1 for my workstation, 1 for backup in my fire safe) and I wanted to protect my eBay account using them, but eBay only offers me options to add SMS or eBay's mobile app as 2nd factors.