i found out that my problem was a 5 block update file that may or may not be left over from an older smash update that was like the first thing in the list of additional content.
apparently, fbi checks if you have the right updates before installing dlc cias, and that little thing was in the way, preventing it from understanding I had the latest smash update already.
after i removed that 5 block update through the system settings, i could install the dlcs. (though i have yet to start the game and see if they actually applied)
those tiny files do take surprisingly long to install though
talked too soon. smash doesn't recognize the dlc
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ok, i ended up removing every smash file including the big update and installed a cia of said update, after checking if the update cia actually applied, i then installed the dlc again and it finally worked.
kinda weird, but oh well.
i also used bigbluemenu this time.