This 2FA FIDO2 FOSS YubiKey alternative is an interesting project I stumbled upon a while ago. In no way is it a fair project, apart from being fully (?) open source.
Instead of buying a YubiKey 5 with NFC for 50 EUR (no longer FOSS since YubiKey 4) I decided to back this project instead. For me, it was ~39 EUR for the NFC one and the one without NFC. Expected delivery in Feb 2019, but if you buy the one without NFC delivery occurs in Dec 2018. They also have USB-C optionally.
As soon as I have one, and there’s demand, I can post a review or share my experience with the device. Though before that happens there might already be reviews around.
Its available on Kickstarter though, so its a toss up whether the project will succeed.