I feel like a very obvious answer here is the existing author commentaries (once you've read through a first time or if you can have someone filter them to you sans spoilers if you are on your first time), you can very clearly see hussie begin to hint at and play with the ideas that would and did become the epilogues and post-canon and I think if we ever do get them for the latter half of homestuck that trend will probably ramp up even further, I genuinely would not be surprised to see ones really laying out for the reader the seeds of jane and dirk's post-canon heel turn or more discussion of what the ultimate self is.

Otherwise ppl here have recommended a pretty good body of works. Uhhhhhh... good musical with some metanarrative themes is into the woods you can see that free on youtube.

Otherwise my main recommendation for "extra credit reading" is like, read through homestuck a second time intentionally looking for literally anything that could be part of a trans reading for various characters. Find other people who are reading it and compare notes with them. Do a book club even with a focus on teasing out as much transgender analysis as possible this is not a joke I don't care how stupid one thinks the evidence they've found is even "hammers are phallic objects and john allocates them to his strife specibus before being told that allocation is permanent and being annoyed by that and later we also find out specibus allocations are not actually all that permanent" can be a good place to start.