There's an series of codex entries on Avikan history, and a series on Rhadeis, which mentions some things about the involvement of the Centens in the Avikan's development, but there's nothing to be found about their evolution before all that yet, at least not online. I'll try to write more about this after the hotfix is out!
As for the Trinkain intro mission, they get a couple of radio messages from an admiral of the Elithian Alliance when they beam down to their first planet, which is actually a quest that's hidden from the log, but there's no mission like that of the Avikan yet.
In a future update, there's going to be another outpost - one for all races belonging to the Elithian Alliance - and the Trink will get a mission to visit that too. I'm also planning to add storylines with full-on missions for all races in the future, but that's going to take a long time to build.
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