Deploying to Heroku should work regardless of where you host your code as the Heroku CLI adds it’s own git remote for the sake of deployments. In fact, you can even git pull from Heroku, so you could technically use Heroku as a private git repository instead (though not recommended). As for using the GitHub client to connect to bitbucket, simply change the repository remote to the URL provided by bitbucket in the settings tab of the client.