Submitted URL not selected as canonical: The URL is one of a set of duplicate URLs without an explicitly marked canonical page. You explicitly asked this URL to be indexed, but because it is a duplicate, and Google thinks that another URL is a better candidate for canonical, Google did not index this URL. Instead, we indexed the canonical that we selected. The difference between this status and "Google chose different canonical than user" is that, in this case, you explicitly requested indexing.
Don't forget about pdf or email URL of "news". Your plugin will not generate canonical links.I forgot. It will be added some new versions :) Maybe, so little time.
For example by comparing core prefs URL settings with a request.Yes, but there must be some system (logic) in URL settings, each part works differently. Nightmare.
I will add a new relational table between canonical URLs and gsitemap table.Yes! exactly what i thought. Only this way.
Just playing with google custom search. It's searching this site, e107.org and github with e107 in repository name.
If you use any my theme: with version 2.2.0 there are core changes - comments and social icons - if you find problem, just tell me.
I will be on holiday until end of November. So no answers from me until then.