Vaultwarden is an open-source password management server option that implements the Bitwarden server API which makes it compatible with all the existing client applications and browser plugins.
Since the Bitwarden feature-set is pretty darn good my hope is that some foss "bitwarden-api" client applications come along and that'll offer a more independent solution.
Argh. If only there was a decent cloud-based open source alternative that worked on Windows, Linux, iOS, macOS, Firefox and Chrome.