If you're looking for something to buy, look elsewhere.. Linux is FREE

If it's not in the repo he could just as well install another distro which supports it

If it's looks and customisation you want, search KDE plasma on YouTube

I think it might have to do with the lock screen. Try locking the screen while audio is playing and see what happens. If that is the case I think there might be a workaround that involves reverting to the old lock screen or something. Hope this helps..

Probably how many devices that can run the service at the same time.. Within the same household presumably

Is running Linux from a USB drive an option! You don't have to install anything on the machine itself, and you could run the pen drive os on any machine..