wix.com – How to set a default site on wix?

I’m unfamiliar with wix and am trying to help my wife with her site. I noticed that <whatever>.wixsite.com results in a page not found error. You have to supply the name of the home page after the domain in order to get to her website.

I’ve looked everywhere I can think of in her settings to set the default so that the domain goes directly to her site’s home page. I used to do web stuff over a decade ago, so I’m surprised it’s not obvious and that searching their documentation doesn’t immediately reveal how to set this default. So I must be missing something obvious. Can anyone help me out? How do I set the default page?

Like, is there some undocumented page name (e.g. index.html) that will prevent the domain address to result in a 404?

Note, we already worked-around this issue via a paid domain name that redirects to the full URL of her home page. So I’m only wondering specifically about a default.