Since chrome support for FIDO U2F was added some time ago but now other browsers like Firefox support it as well. While it does work if enabled manually on older firefox versions since Quantum, current version has it enabled by default. It indeed works with Yubikeys on their test / demo site. However it does not work with AA.
See https://www.yubico.com/2017/11/how-to-navigate-fido-u2f-in-firefox-quantum/
by: Paul M. | over a year ago | Supported Platforms
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We will investigate this. It is in line with our roadmap.