I moved my small free Python/Django app to Fly.io and am extremely happy. The move was seamless because they allow you to run your app from a Dockerfile which was straight forward after going through the documentation. Looking forward to building more things on Fly.io.
I'm planning the migration with my Django side projects from heroku to fly as well. Fly has a special org on GH with example projects, but the one with Django is empty. I created a small test repo to see how Fly works. hands on. Thought I'd share.
Highly recommend fly.io as well; I started an elixir app for a client and decided to use fly.io and very impressed with how easy it is with the feature set so far.