@December You mean energy bending? That's an avatar exclusive.
I'm pretty sure you're referring to the Spirit Gurus I mentioned, and actually, there is a large variety of energy manipulation that non-Avatar characters have performed in the past. From the Banana Guru Aang encountered at the Western (?) Air Temple (I really don't remember which one), who led Aang through a spiritual journey to unblock his Chakras (granted, he never directly performed any energy bending), to the spiritual powers of entering the spirit world (I would say Tenzin but, y'know, he never did), to Jinora's astral projection powers to even Unalaq's spirit manipulation powers. Manipulating the spirits is typically seen as an Air bending ability, however, that does not limit it to a single element (@Unalaq). Even when Korra was attacked by a spirit in the middle of the ocean when she was being chased by Desna and Eska, she washed up on a Fire Nation island where a spiritual fire bending guru was able to discern what was happening to her spirit by use of fire bending.
@Regitnui Well someone did their research. XD
If we were to go ahead and place ourselves in the time of an Earth Nation Avatar, I think some things would be different regarding technology. I'm also just now realizing I never finished the last season with Kuvira. Idk why but I stopped around the time of Kuvira beating Korra in a 1v1. I suppose I can't say much regarding technology because I don't know how the spirit vine harvesting ended.
Do you guys think there would be artificial bending at that point? We already seem some rudimentary forms of lightning bending in Asami's lightning glove, as well as faux metal bending in the magnets Asami's father employed. Hell, there's even fire bending gadgets among some of Amon's radicals (the flame thrower guy).
I don't think it would be too hard for them to replicate bending in that era (excluding earth and water bending). For fire, they just have fuel tanks on their backs and gloves and boots that can expel fire. Air bending would be more difficult to replicate as it would require manipulating the air pressure by either having tanks of compressed air that would expire quickly or giant fans. Earth bending wouldn't really be possible, but magnets faking metal bending would. Maybe lightning gloves would be ranged by that time.