Theoretically, the Dockerfile should "just work"™ with Render.com as well. Right now I focus on fly.io only because their free tier offers PostgreSQL without time limits. Render, I believe, only does so for a period of time.
See here: https://github.com/silviogutierrez/reactivated/blob/main/dev...
https://github.com/silviogutierrez/reactivated/blob/main/dev...
https://github.com/silviogutierrez/reactivated/blob/main/dev...