The setup I'm describing would just be incus running on the Debian host. You'd then spin up a VM with incus and run Docker Swarm inside the VM. Yes, there's a little bit of overhead with running the VM, but it's pretty minimal and makes it a lot easier to backup your whole server (since it's a VM) verses trying to backup a physical server.
You can run all of your containers in this incus VM. Yes, you could just run containers on the host but this setup makes it easier to keep everything self-contained IMO. Also, maybe you'll have a need to do something in the future that can't run in a Linux container (e.g. a FreeBSD server), so having the ability to spin up VMs and not only containers is useful
I'm self-hosting Obsidian as described below and it works really well. The syncing happens automatically in the background and I rarely encounter conflicts. I'd highly recommend it! https://avidandrew.com/elevate-your-note-taking-with-obsidian.html