We had originally planned to go all-in on passkeys for ONCE/Campfire, and we built the early authentication system entirely around that. It was not a simple setup! Handling passkeys properly is surprisingly complicated on the backend, but we got it done. Unfortunately, the user experience kinda sucked, so we ended up ripping it all out...
It could be your browser / system that is struggling to show it. When I use my work computer and Microsoft edge, I don’t think I’ve ever had a situation where the QR code didn’t work. When I use flatpak’d Firefox on my Linux laptop, I experience more trouble, probably because of the sandboxing.
According to the device support page i should be ok, but yeah there might be something weird going on.