Looks like that still has downtime for a Postgres migration- you're suggesting going into maintenance mode and just doing a dump/restore. I've seen that take hours once you hit the terabyte scale, depending on hardware.
I've had pretty good luck setting up logical replication from Heroku to the new provider and having a 10-15 minute maintenance window to catch up once it's in sync. Might be worth considering.
You might also want to add a warning about Postgres versions. There's some old bugs around primary key hash functions that can cause corruption on a migration. I've seen it twice when migrating from Heroku to other vendors.
Sorry, but telling people to take a logical backup of their database, and then download it onto their local work station is insane for a production application. First, a logical backup at any decent scale will fail, and second, I don't even have enough local storage to do that -- even ignoring the compliance issues with downloading a full copy of production data onto a work station.
For a company like Northflank, I'd expect actual production-grade documentation for migrating, not instructions that are only applicable to a toy app.
Some folks want to do that, others want to import a backup directly, some want to spawn a read replica and sync their DB. Different strokes for different folks, all supported on Northflank.
northflank supports the same buildpacks that you run on Heroku, so it should be fairly straightforward.
we have these docs for a more detailed walkthrough:
1/ https://northflank.com/docs/v1/application/migrate-from-hero...
2/ https://northflank.com/blog/how-to-migrate-from-heroku-a-ste...