He mentioned partitioning bare-metal into VMs (which is a good idea, containers aren't a great security boundary) but it doesn't look like MRSK does that (yet?).

I can see using this to deploy on DO or Hetzner to save a few bucks vs Render or Amplify- but on bare metal you're giving up a pretty amazing ecosystem these days. Ie. if you want to run stateful things like databases, logging/monitoring, NFS, object storage, persistent disks, complex networking, etc it's going to be miles easier to manage that w/ k8s. Even for that bare-metal/vm-partitioning goal above, there is a k8s runtime (kata-containers) which will automatically run containers on lightweight vms and handle all the plumbing to and from K8s. Plus if your mid-size SaaS wants to sell to the whales you're going to need compliance and security best practices that are much easier to implement and enforce w/ k8s. Finally, there are also lighter weight distributions these days to make it less painful to run yourself.

That said, I do appreciate the 37signals philosophy of having such strong opinions they craft their own tools and I also applaud leaving the cloud for bare metal. Even if you need the burst capacity you can provision your base-load on bare-metal and burst to the cloud when needed.