No matter how you try to spin it, Nadal is terrible indoors. He has 2 titles total in his career indoors and I think one was indoor clay.Let’s not act like Fed has no holes in his resume. 10-21 against Djokodal in slams, missing 2/3 modern clay swing masters, likely to hold no major record within the next year etc.
Undisputed Clay GOAT by miles + McEnroe’s career off of clay is more than enough to be the arguable goat.
Being GOAT is about being great across ALL conditions, outdoor hard, indoor hard, clay and grass. Nole and Fed have racked up titles on everything and greater across all conditions (notice I'm using the term conditions as Nadal fanatics will go berserk about indoor not being a "surface" so it doesn't count).
Bottom line, Nadal will go down as Eternal Clay GOAT and Overall GOAT will come down to Fed and most likely Nole.