Hide sidebar on user pages

I would like to not show the sidebar on the pages that show a user’s profile (eg: https://www.designwall.com/question/?user=nobita).
In order to do this, I wanted to simply use a different page template when displaying a user profile.
How can I do this?
How can I use a different template when displaying a user’s profile?

Update:

An even better solution would be if all user pages had a different url (eg: …/users/…) rather than just the same url as the questions list page but with a query var (eg: …/?user=[someuser]…).

Is this possible?
Thank you.