Firefox Passkeys not working - all passkeys generated in firefox android are instant lost.

I use Firefox Android and Bitwarden Password Manager. When I try to generate a passkey for some website Firefox asks me for the device to store the passkey. The only suitable Option is "This Device". When I tap it, i am asked for authentification (Fingerprint). After Authentification the website gives me a success message and the whole process is complete but the passkey isn't stored anywhere. In every other browser on android I am asked for the entry in Bitwarden where the passkey should be stored. On windows this works with Firefox Is it intended to work only when passkeys are stored in Firefox itself? At least a hint that it doesn't work with external Password Managers would be helpful - lost passkeys are a pain