Trying to run the starter kit, it tries to download mkcert, but that download fails with a ssl.SSLCertVerificationError... how ironic :)
brew install mkcert fixes this.
Also, a starter kit that asks for my password right away is a bit too intrusive for me:
    Downloads/new-project [master {origin/master}|]: uv run plain dev
    Generating SSL certificates for app.localhost...
    Created a new local CA 
    Note: the local CA is not installed in the system trust store.
    Note: the local CA is not installed in the Firefox trust store.
    Run "mkcert -install" for certificates to be trusted automatically 
    Created a new certificate valid for the following names 
     - "app.localhost"
    The certificate is at "/Users/me/Downloads/new-project/.plain/dev/certs/app.localhost-cert.pem" and the key at "/Users/me/Downloads/new-project/.plain/dev/certs/app.localhost-key.pem" 
    It will expire on 29 June 2027 
    Adding app.localhost to /etc/hosts file. You may be prompted for your password.
    Password: