Some of the best guides for retro games out there are super obscure, hosted independently, or only still exist on the internet archive. I know a couple, but maybe we could make a big list.
The Princeton Guy's Let Us Cling Together: Tactics Ogre: Tactics Ogre comprehensive guide site. This is the most complete guide to the original Tactics Ogre in English that I know of. New remasters of the game have made this more obscure even within the SRPG community.
Beat'em Up Dissection: This web series is one of the best documentations/ genre spanning strategy guides ever assembled. There's knowledge here that you only see replicated on Games Done Quick and other niche communities. Look at those VIEWS. I am going to download the series just so I know there's a copy out there.
I'll add more when I think of them AND YOU SHOULD TO IF YOU KNOW ANY
RPGshrines is one I've used, I like this one for Aria of Sorrow here https://shrines.rpgclassics.com/gba/cvaos/walkthrough.shtml
that one is great, i just used that a few weeks ago for my RA run through that game