At least with Vaultwarden, it's open source and running locally with data stored on a server in my house, so if they misbehave, I could easily fork or switch projects. If Android doesn't allow or otherwise hobbles 3rd party password managers, there isn't much recourse.
That's fair, but Bitwarden itself is also open source... though, my understanding is significantly more difficult to get up and running than Vaultwarden.