Interesting that my interpretation of a clean install is that there are as little packages messing with each other on the main install. Therefor an immutable distro is very good in this regard. Moreover, for a clean systme I prefer flatpaks. Packages that aren't available are installed via distrobox. Only system applications are allowed to mess with each other. A download manager isn't that close to the metal that I'd prefer installing it directly. Flatpak all the way.