Rom hacks that feel so FE6, very simplistic, no complex features like skills, yknow just purely classic GBA FE gameplay as it can get.
call of the armor keeps things fairly simple and it’s a good time throughout
The Second Scouring is as FE6 as it can possibly get.
Celice
5
These two feel kinda like what is being described (to me):
Sword of Heaven and Earth has really fun level design that often feels very authentic to early FE games.
I also recommend the Midori patch. I don’t remember it having too many new features like modern FE hacks, and focuses more on gameplay.
Both links are for English translations.