I got into My Hero Academia sometime in mid-2018, when the anime was still very early in airing (I believe it was only up to season 2 at the most). With Dragon Ball having been my only real special interest up to that point, it served as a REALLY fascinating mentality shift, both because it was the first thing to actually come close to dethroning Dragon Ball and becuase its characters and power system very quickly felt far more depthful and engaging to me. Not only was the show itself very compelling from the early stages for me, but there was a shocking amount of fandom content even when compared to Dragon Ball --- did you know that there are magnitudes more fanfictions for MHA especially, despite being out for a fraction of the time? Last I checked it was almost 400,000.
If that wasn't enough, the existence of the MHA Vigilantes spinoff was even MORE content and worldbuilding that I could actually engage with, and in a lot of ways I almost found Vigilantes more enjoyable than the main series (at least, the latter portion, which I'll explain momentarily). There's just a very undeniable wealth of content to explore, and over the half-decade or so I've engaged with the series that has allowed it to never really grow stale for me.
For me, the elephant in the room is frankly everything in the War arc onwards, as this is when (to me) the writing quality began a steady downward decline that meant I was mostly reading along for the sake of finishing what I started, as well as the cool moments scattered throughout. Things definitely got a bit shaky towards the end and I have a lot of complicated thoughts about the ending chapter(s) as a whole, but even with all of that in mind I absolutely still reccomend MHA to people and I still enjoy it myself.
With the wealth of fandom content and AUs it's likely unsurprising to find out that I have several AUs of my own. Frankly, I have AUs built upon other AUs at this point that then use "isolated" content that doesn't really belong to any of my AUs as additional frameworks, which just kind of shows the level of interest (or obsession, take your pick) that this series has managed to foster within me even over half a decade later. All told, MHA probably has the largest number of AUs in the most "complete" state out of my media I engage with. I have to put complete in quotes becasue very few have details outlining all the way to a story conclusion, but there's certainly far more to chew on with them than my dozens of abandoned Dragon Ball fanfictions scattered on various old Fanfiction.net accounts, at least.
Oh boy, this one's gonna be just a bit of a doozy.
So I have a LOT of MHA fan content, and while some of it is full-on AUs, others serve as 'AU frameworks', which I can use interchangeably to make the creation of new AUs easier (IE, if I want it to be a college AU, or if I want it to use specifc interpretations of quirks that I've created in my writing over time, etc.), so I'll be trying to split-categorize these different types of fan content as clearly as possible.