Currently, Bitwarden's autofill feature does not work reliably with Waterfox on Android, as it only displays login credentials associated with the package name net.waterfox.android.release. This is due to Bitwarden allowing autofill for website URLs only in whitelisted, privileged browsers on Android.
The Iceraven browser faced a similar issue and successfully resolved it by getting their package whitelisted, as shown in this pull request: bitwarden/android#4122