@Lucatermite @bearfree hi! I only know the El Chalten area very well so can only advise about that. I am also not an expert on bikepacking. I would think a good trip could be worked out from El Chalten heading up past Lago Desierto to the north and then onto Lago Villa Higgins. Boats could be used from there (Candelario) to access the other extensive areas north of the lake.
I would guess there are endless opportunities for you around El Calefate too and the land between there and El Chalten.