https://ethereum.stackexchange.com/questions/145082/error-of-add-custom-app-the-app-doesnt-support-safe-app-functionality

I made a template with a command in the repo:
https://github.com/safe-global/safe-apps-sdk/tree/master/packages/cra-template-safe-app

After yarn start,
I added localhost:3000 at ‘Add custom app’ in the gnosis UI,
and got the error: The app doesn’t support Safe App functionality