the fact that you worry about that says you're already doing better than most people :)

my kneejerk reaction to people complaining about things is also to propose solutions, and i've only relatively recently realized that often people complain as a way of venting stress/other emotions, not as a request for ideas. i've found that bluntly asking if people are looking for support or just trying to vent works wonders, although YMMV if your friend group is less neurodivergent than mine. an offer of a hug is a good option too :)

wrt to your trans friends, honestly the best help you can give in most situations is just treating them as their preferred gender.