(Assuming we’re talking closer to the crush stage) (Got a little too big, so putting them under details)
Lucas/Nat--they're both adults
Lucas (Nat) would… probably feel a little envious. They aren’t officially a couple, but the feelings are, if nothing else, sort of out in the open. He would try his best to sit back and observe; they’re both adults, right? If the other guy did try to do anything stupid, he’d step in and warn him off gently but firmly.
Lucas/Ava--falling in love with a defrosting ice queen is never easy
Lucas (Ava) would be stuck in two competing feelings. On the one hand, he hasn’t exactly been open about his feelings, although he is honest with how much he enjoys being around Ava. The L word is a complete non-starter at this point; he’s no fool, and (assumes he) knows it won’t work with her. On the other hand, his unconscious feelings didn’t quite get the memo. So, a lot of confused envy blended with self-doubt, unless she was open about the other guy backing off.
Renard/Farah--More than willing to give this a try
Renard (Farah) would… It would be a bit much to say that he’d be better at it than A!Lucas, but there would be less envy in play. Definitely some questioning as to how Farah would handle this, but he’s sensing that there’s more to Farah than meets the eye. And he’s open about him liking… whatever this is they have going on. He’s more than willing to hear her out.
Eric/Morgan--the reformed hacker just can't get rid of some old habits
Eric (Morgan) would have difficulty swallowing feelings of frustration and envy, although Morgan becoming more focused on him would make things easier to deal with. He’s a little dubious about if this is going to work, but there’s some sort of bond that the two of them seem to have. He wants it to work out in the end.