After some practice and learning I have managed to make "good run", collect many logs and done the objectives.
Or have I? I have done some googling, after all the objectives ceased to give me something to do ("Unable to determine further course of action.") As for this wiki:
[url=https://duskers.fandom.com/wiki/Category:Objectives]https://duskers.fandom.com/wiki/Category:Objectives[/url],
I have all the logs listed. Yes - all of them: all for every objective, the "Hey You", and "unfiled".

I am missing something? Have I already missed something?
What to do now? I was checking derelicts one after another, but it looks like it will only allow me to keep flying and not give me any more knowlege about what has happend.

Late reply, but if you've confirmed you've gotten all the objectives then yeah, you've pretty much finished the campaign. As for what happened, you'll have probably noticed that as each objective chain is finished, it ultimately intersects with one or more of the other theories in subtle ways. On the one hand it'd be good if the game gave you a clearer signal that you've cleared all the objectives, but on the other hand, I do like how the game lets you piece together the conclusion on your own, and shows you what happened rather than just straight-up telling you. Great bit of immersive, active storytelling, if a bit of an anticlimactic bummer when you realize there's nothing left to do. I can see it both ways.

The dailies and weeklies are a blast though, lots of folks who've barely touched the campaign have stuck with the game for years, just playing the dailies.