We have many SXA sites in our instance and want to configure each site to have its own 'LayoutNotFound' Url. Is there any ready configuration/field available with SXA like 'Page Not Found Url' field specific to Site.
The easiest way to do this is to enter a relative url in the
LayoutNotFound url setting. So
/errors/layout-not-found and then create a convention that puts the layout not found page in the same place, with the same name for each site. Its not perfect, but it should give you the required results. If for some reason, you want a different Url per site, then you will have to implement a custom option for that.
Take a look at
LayoutNotFoundResolver processor in the
HttpRequestBegin pipeline (depending on your SXA version).
This is a custom SXA processor which at the moment should redirect you or transfer (base on
Settings.RequestErrors.UseServerSideRedirect setting) to 404 page (you can define it on your Settings item). Feel free to customize it so that you will be able to select a page base on the current site.