Does Karma trigger off of recycling cards into other players’ Main Deck due to a card like Sabotage?

No. The updated rules will clarify that regardless of who is instructed to do the recycling in card text, players always recycle their own cards. To reflect this, Karma is receiving errata. [Vision] (When you play me, look at the top card of your Main Deck. You may recycle it.) When you recycle one or more cards to your Main Deck, buff a friendly unit. (If it doesn't have a buff, it gets a +1 [M] buff.)

Related: Karma, Channeler, Sabotage