Here's where I got it from: https://doc.owncloud.com/ocis/next/depl-examples/ubuntu-comp...
And I wish it was "containerized" but really it's "dockerized" as this thread demonstrates: https://central.owncloud.org/t/owncloud-docker-image-with-ro...
So yeah like I said in my original comment, for personal use it's just not right for me (because I choose not to use docker in my personal projects), but I hope it's right for other people because it looks like a killer app.
I'd definitely like to see what other options are available on other distros so I'll dig through their documentation more.
Your second link appears to be about OwnCloud, not OwnCloud Infinite Scale.
I think what you're looking at is: "Here's an example of installing this on ubuntu 24.04. These instructions will also work on 22.04." This is in no way saying they can only get it to work on ubuntu; they just haven't written a step-by-step example like this for other distributions.
And yeah, trying to use podman with something that's based on docker compose is ... probably gonna give you some headaches, I'd guess. I don't particularly know the pitfalls but if you're expecting it to be transparently swappable, I don't think that's an owncloud issue.