I pointed a new custom domain to a Google App Engine Standard Environment project and edited the DNS records per Google\'s instructions, and it seems to be redirected proper
You'll end up with something similar that originally brought you to this solution:
App Engine Settings With Domain Name SSL Certificate Not Working
Fill in the info with the appropriately matching IPv4/IPv6 addresses:
Custom Resource Records Where You'll Copy Over Info From App Engine
** Precaution: This is for domain names bought through Google's registrar. If you bought yours elsewhere then the steps may differ.