Not sure where everyone is getting this from when my interpretation was that L3 was clearly projecting her own "feelings" in a tsundere manner and that Lando didn't view her as anything more than a droid and friend.
https://io9.gizmodo.com/lando-calrissian-is-pansexual-1826116231
I wish that were true, but considering droids are specifically mentioned as part of his sexuality here and L3 mentioning his heart rate going up when near her, I don't think that was what the screen writers were going for. Also he ran out into almost certain death to get her back and was completely devastated when she dies. Sure it could just be friendship, but it very much felt like the movie was going for something more.
Sure. That doesn't explain why Lando doesn't.