If I hover over a building or some techs in the tree I can't see what effect they give I only see how much upkeep they cost.

Yeah, it’s the most annoying bug that has been unsolved for some years now. It is triggered by hovering over certain techs in the tree, and you should be able to display the full tooltips again by hovering over certain other techs, see this post.

But the quickest workaround is to immediately save when you start a new game, exit the game, restart and load the save file and it should be fixed for the remainder of that playthrough (just reloading without restarting the game isn’t enough if I remember correctly).

Having said that, I just tried to recreate it, started a new game and the bug was not there. Maybe I just got lucky and it doesn’t always appear. The only noteworthy thing I had done since I last encountered the bug was deactivating all DLC and reactivating them at a later time. It’s a wild stab in the dark, but maybe try that and see if it fixes things. In the meantime I had started a game without DLCs and without the bug, so I assumed it was introduced by one of the DLCs.

made an account and found the forums just to post about this stupid bug. I am able to recreate by typing anything into the research tree search bar. This hides system tooltips and info on buildings. Very annoying. Easy fix is to just press the X and clear the search bar in tech tree. 

Please fix this. so many bugs, very fun game but so many bugs, so many unexplained mechanics.