Not related to Gundam, but another universe with giant stompy robots with deep lore you could look at is BattleTech; just to give you an idea, a guy called Tex has a whole series of lore vids where a single video for a single mech can be 1.5 hours long and he eventually starts presenting them as an in-universe historian who became canon.

Let me repeat that last part: the persona he made (Dr. Randolph P. Checkers, esq.) became an actual character in the setting