I mean, sure. That’s not at all unexpected. But not even allowing the user to try at all, or making it unreasonably difficult to try, is very frustrating.

Place the option behind developer mode, with a disclaimer that features may fail and Mozilla makes no promises or guarantees.

But just flat-out denying the option, or making the user jump through ridiculous custom collection hoops is nonsense. In my case the custom collection method still failed, but the extension I was looking for does in fact work just fine, after installing it with the modified user agent string.