How do I talk to minor races now?

You don't.  Brad said in the Discord chat that he made them "speedbumps" for the player.  You can't talk to them, you can only send freighters to their worlds.

OK I seems that I will want to send transports rather than freighters. Trade has really been nerfed now and doesn't bring in much cash and I don't see a diplo benefit when trading with major races.

Hmm...

I think that I don't like this change.

implying that minor races are only capable of being speedbumps and nothing more implies that the only thing valuable about them is their worlds to absorb.

.... Benevolent races aught to be able to get a bonus in trade, or diplomacy for "uplifting" the minors rather than destroying them. 

I'm also not a fan of this change. I loved to watch as minor races went about their business. I remember at least one game where a minor was nearly as important as any major race.

I played Crusade for a bit, didn't notice.

There should be diplomacy techs that can assimilate minor races into your empire with bonuses. Basically similar to Civ 5 city states.

Minor races can only have one ally. After allying with major race for X amount of turns you can assimilate them.

depends on your play style. On a medium map after a while I'm getting 15 cpt for each trade route. That's as much income as a planet that is not Econ optimized because raw production is much lower overall

Think I'll hold out for a 'minors as majors' mod. The more, the merrier.

It is a nice idea but as I understand it minors are on the way out.