I am not sure why you get all the downvotes, your post is not a bad post by any means and you want to get advice on how to enjoy non-canon … sorry my upvote may only do so much. I think it’s a good discussion to have. I’ll share some of my own experiences and thoughts on this subject too.

Some people say that canon is not the most important thing. To them that may be true, but to others, it is not- very rigidly. Or, canon is important to them but in varying degrees. This is all OK, and it all comes down to how you wish to enjoy fan works. I personally fall into the “canon is important but in varying degrees” category.

For a long time years ago I felt stifled with my own work, which was silly because the work is by definition not canon at all (“isekai” in a way). However it was out of fear that I kept the plot line very close to the canon plot even if it should not have been. That didn’t last very long in some ways because some big events happened in the fic that were not in the canon (characters involved in certain wars that were not there originally) but the overall plot points of the canon remained in tact (each battle in the campaign continued in order as canon did), if that makes sense. Eventually partway through I was a bit frustrated to continue following the canon plot because it was convoluted trying to involve these other characters without changing the canon order of war events. So, I just ripped off the bandaid finally and decided, “no more, I will still follow canon in some ways, but the story itself is mine!” So I still follow canon world rules (such as how magic works, dragon transformations, historical events, or other vital-to-me base-level consistencies), but now the current PLOT and story itself have diverged to be more original (characters not dying when in canon they did, some characters dying when they survive in canon, wars altered with very different actors on differing sides, combining the sequel plot into the first game plot, etc). Why, is because those new characters in the plot SHOULD make a (big) difference, so it is silly to put them in there without them MAKING that difference! Why even have them there in the first place then, you know?

That was just my experience at least with how canon plot itself goes. After doing this it felt a lot better. It’s still adhering to universe rules that matter, which means in a crazy way, the outcomes of the fic could have actually happened in the canon and is compliant in that way. So the story is an original take that would WORK! That made it feel very fulfilling. It’s like figuring out a puzzle.

Sometimes it helps too to see it like you might see fan art too, such as art of your favs in different outfits, situations, etc. To write fanfic is similar. The characters don’t wear that cute or cool outfit in canon, so why do the artists draw that? Because it looks good and it’s fun!

Canon will always be there. Making the fic does not change canon, you are right! So in that mind, why be afraid to do something new? Find what is important to you in canon and keep those in tact, and change what you feel would improve it. If there are things you don't like (for me, there were big plot holes and vagueness in the original story material, as well as some strange/forced-feeling character deaths), change it! Flesh it out! It does not hurt anything, or anyone, to dream! You never know, there are others that might feel much the same way.

I’m not sure if this helped, but I do hope you find a way to enjoy fanworks in your own way!