It's somewhat locked down as you need to apply with Microsoft for a Developer account, but you can technically sideload UWP apps onto your Xbox hardware by entering Developer Mode. https://learn.microsoft.com/en-us/windows/uwp/xbox-apps/devk...

It's not convenient and you need to reboot your console to go back to running commercial apps, but it is present. At least it's a one-time payment to get the developer account.

How is that at all different from what you could already do with Apple devices?

And what percentage does Microsoft charge for games on the Xbox?

Would anyone who's calling for iPhone sideloading be upset about Xbox sideloading? I wouldn't. By all means, let's regulate both Microsoft and Apple. The more the merrier.

I don't think I've ever looked at a video game console and thought, "I'm sure glad that I can't sideload games onto this." This is a slippery slope that I am happy to go down.