@grb I remember that discussion in general… and as I don’t know an answer to the question you posed (for the device-side)… according to the Help Sites, U2F keys should be recognizable (“marked” as Migrated from FIDO) in the web vault:
(–> https://bitwarden.com/help/setup-two-step-login-fido/)
PS: Okay, as far as I remember that discussion, it remained a bit unclear, what kind of credential really get’s created in the now-called “passkey”-2FA-option… but I would think that, nevertheless, no “old” kind of “FIDO1” credential that in 2025 get’s invalidated, can be created since maybe mid 2021 ?! (PPS: Or am I too naive, again? 
):
