I've had luck exploring the upstream's source repositories. Often, 'official' charts are in the repos, but not pushed anywhere. Also, if you aren't averse to Bitnami, they've quite a large collection of charts and applications which receive care and maintenance.

Sometimes people build their own helm charts on GitHub, but not sure if that will qualify for "trusted".

You can make your own, if a project has an official docker image, it'll just be a matter of writing a deployment.yaml with that image,, a service.yaml for the deployment and possibly a pvc.yaml just to give it some persistence storage. Its what I do if a project doesn't have an official helm chart.

Not as far as I know. The only option is usually looking in Github if someone did already the work, but that's not trusted...However, I usually just run Helm template command to see what manifests get rendered, so it's not too hard to establish trust.

In my experience also chart writers tend to be quite generous with permissions (for example, providing a ServiceAccount even when not needed), so I end up tweaking the charts very often.

Artifact Hub might be what you’re looking for?