There are some exciting ways to continue using the heroku build packs and Google cloudbuild to host on gcp. You can maintain git push deploys costs can be pretty inexpensive. The primary cost is around managed postgres.

https://cloud.google.com/products/calculator#id=46eb44ca-9ac...

It isn't the same as a free plan but can provide a very similar ease of use. My profile has contact info if you want more detail.