Ding. Canon debates are always stupid, because the concept of canon and continuity only matters to a single group, the fans. If the fans decide a story isn't canon and don't discuss it as canon, then effectively in every way that matters, it isn't canon, and you often later on see that reflected by the "official" writers of the show as well. All canon by it's very nature is headcanon and even in Star Trek we've always seen this as yeah something is "Technically canon" but completely ignored by the fandom to the point you even get arguments about it's canon or not (Sybok and STV for example).
I suspect in 5 years time, Discovery will be treated as it's own thing by the fandom not part of the Prime Universe, hell it already is now by much of the fandom, so effectively, when discussing it in those spaces, it will just be an unwritten rule it's not prime canon and thus, while you are in those spaces, it effectively won't be canon, because again, canon only matters to the fans.