Reliability: It’s not great

For django, they should really contribute to 2 scoops django cookie cutter program, so that you can get an out of the box django instance that can just deploy to Fly.io.

May be wrong, but they seem to be very focused on interesting stacks like Elixir and RoR while building on Go/Rust. The corollary being neglect of the bread/butter stacks with high market share, like Python and Java/JavaScript. Don't think I've seen a blog post discussing those three beyond a passing mention?

Not the end of the world, but mildly disappointing. At least they are all in with Postgres and Linux, a great foundation.

I thought the only thing their tech stack was all in on was docker images being rewritten to run on firecracker as a substrate.

is it not agnostic about things like Elixir etc, at the tech level, though they've got super nice documentation for those tools you mentioned?

What's necessary to change for them to run on Firecracker?

Here's a post explaining how they do it https://fly.io/blog/docker-without-docker/