@justforthelulz
Despite official confirmations and etc, it's generally easy to tell when a manga is canceled internally vs. it ending naturally. There are dozens of mangas out there that, when you read it, you can tell they got the 'ok, polls are bad, you only got 3 more chapters before you gotta end this' treatment.
A manga according to mangadex/mangaupdates that is officially canceled is when there is an exceptionally abrupt end where the manga doesn't get the usual 3 more chapters and is just forced to stop, even if there was a 'to be continued' in the last chapter or a teaser in the last jump edition for example. Some reasons can include political like in the case of Keijo, or author's death, which does happen and made me pretty sad for a certain series I currently forgot the name of.