I’ve seen a few people asking about NFC readers for authentication in the expansion slot - but I don’t think any have been made.
The smallest reader I can find is the ACM1252U-Z2. According to the spec sheet, it is 20mm wide and 6mm tall. If the USB Micro female port cold be swapped to USB-C male, it should be able to fit in the expansion slot, right?
The only problem is the length. It’s 52mm. About half that is circuitry - the other half is the antenna. If it were bent 90deg in the middle, it would still be taller than the RJ45 expansion card.
There are things like this little one but that acts as a keyboard rather than a proper reader. So it won’t work with Yubikeys etc.
Has anyone found a smaller reader that could fit and do FIDO?
Does anyone have a pointer to relevant documentation on how the reader should appear to the system? I assume it would be some form of HID device, which is probably what the one in your second link does to look like a keyboard.
I’d LOVE to get an NFC reader. If you can find one that has a separated antenna that is still small, you might be able to fold it over or be creative in wire/flex routing to manage to squeeze it in so the antenna would be towards the keyboard.
However, there’s still going to be some metal bits/etc likely in the way above the card, so that might still interfere. Not sure.