Did you know that all fanfics are, BY DEFAULT AND BY DEFINITION, Canon Divergent? Yep. You read that right. All fanfics are 100% Canon Divergent. Now you are probably wondering why I said what I said and I will go into detail down below:
THE ONLY WAY A FANFIC CAN EVEN REMOTELY BE CONSIDERED CANON COMPLIANT IN ANY WAY, SHAPE, OR FORM IS IF IT IS AN OFFICIAL NOVELIZATION OF THE FANDOM, ITSELF, THROUGH A PUBLISHING HOUSE OR SOMETHING LIKE WEBTOON. AN EXAMPLE OF THIS IS X-Men: A Novelization. ANOTHER EXAMPLE OF THIS IS Batman Arkham Knight: The Official Novelization.
Are there going to be minor differences between the X-Men movie and X-Men novel? Probably, yeah. But the novel is still canon compliant because the authors were asked to make a novel version of everything that took place in the film which, by default, makes it Canon Compliant. About the only way it would not be considered "Canon Compliant" - aka CANON DIVERGENT - is if there are so many differences between the two medias to the point where you might as well consider it to be its own thing (such as inconsistencies, AUs, alternate endings, etc.).
Then we have unique cases like Bleach's Thousand-Year Blood War arc being animated and all of that that being canon because Tite Kubo was rushed (as well as having a lot of health issues). So with him helping and getting his hands metaphorically dirty, as well as stating it himself, means that the animated version of the TYBW arc is 100% canon compliant even if there are stuff that did not show up in the manga.
Think of your "Canon Compliant" fanfics as anime filler arcs. The filler arcs are called such because they never happened in the manga. It doesn't matter how in character, say, Ichigo or Kenpachi or Jushiro all were in the Zanpakuto Rebellion arc ... that's all still considered filler because none of it took place in the manga.
Something else everyone need to understand is that we're not all going to have the same exact views on what we consider to be "Canon Compliant" or "Canon Divergent", so to speak. And this does, in fact, include people loving the same exact character. We are not all going to have the same headcanons. And you know what? That's okay! We just all need to come to the harsh realization that, unless stated otherwise, our fanfics are canon divergent by default. Doesn't matter how IN CHARACTER or OUT OF CHARACTER everyone's blorbos are. Mine included.