For an installation of Apache on Google Cloud Platform, and a range of apps, like Wordpress. I've successfully completed "early renewal" with the steps noted by Bitnami here:
Under, "Step 5: Renew the Let's Encrypt Certificate"
https://docs.bitnami.com/google/how-to/generate-install-lets-encrypt-ssl/#step-5-renew-the-lets-encrypt-certificate
You need to check to be sure the domains you are renewing are matching what was previously installed, see the files at the path "/opt/bitnami/letsencrypt/certificates/" on your server to confirm. You can add a wildcard for instance, by just specifying the --domain option again and including the second domain (as noted on the guide linked above).
Path to this documentation on the Bitnami Docs Site is:
Bitnami Documentation > Google Cloud Platform > Bitnami How-To Guides for Google Cloud Platform > Generate and Install a Let's Encrypt SSL Certificate for a Bitnami Application