I'd also call out that Valve is probably running the biggest managed Linux install base in the world now. They manage the OS and update it. If you really want to get in there and root the thing, you can; you can install other OSes including Windows if you want, it's open, it just defaults to managed.
And they made sure to integrate Flatpaks into their base OS image and the default image ships with the Flatpak market/browser, because Flatpaks can be easily installed and managed without conflicting with the base OS that they are managing... and it works. It really works. Even out of the box and without penetrating their management, you have a lot of freedom, and the fences are just advisory.
I'm sure they're not interested in it but they've got a decent solution for someone to start selling managed Linux desktops and laptops for end-users if they wanted to.