You now can serve your app using localhost (127.0.0.1) with a self-signed HTTPS certificate, which Shopify CLI generates for you.
shopify app dev --use-localhost
Note: Localhost-based development isn’t compatible with the Shopify features that directly invoke your app, like webhooks and app proxy.
More about networking options in local development
If you run into any issues with the certificate generation or have other feedback, please let us know.