That's a big one and I'm sure will be the final nail in the coffin for plenty of people. No reason to use Heroku in 2025, especially for Rails apps (you mentioned Kamal).
I moved my app onto Hetzner + Cloudflare R2 and I couldn't be happier!
https://olly.pagecord.com/migrating-the-pagecord-rails-app-f...
I recommend Cloud66 over Hatchbox which is more production-grade, especially for DBs.
Yeah I'm operating on a shoestring but tbh servers are super-reliable as is Postgres. What even is "production grade"? Read replicas, point-in-time restores etc? For a product that is ~$1000 ARR I think I can live with a bit of risk (I do regular backups of course and have a restore process). Maybe it will bite me in the ass, but I'll risk it :)
Happily using Cloud66 but a strong recommendation for Northflank here. I already had a running cluster there and migrating a very complex Heroku app over only took 20 minutes today. (Would have been 5 if I hadn't screwed up .gitignore...)