Fly.io is a reclaimer. Also see: Vercel, Digital Ocean, Dokku, Netlify, Firebase, Engine Yard, OpenShift, Appfleet, Github Pages, Render, AWS Amplify.
Heroku made it easier to deploy, but now it feels a tad bit bit more frictional than other services, including fly.io and these mentioned above. It is probably a bit outdated in that regard.
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