If Mueller found something that was worthy of indictment or impeachment, he would have explicitly said that, instead he said he would not come to a conclusion on whether he did or didn't. Just because he cannot indict a sitting president does not mean he can't suggest that it be done, or suggest that impeachment process should be started based on his findings and his understanding of the law.
Basically, I read this as, he still thinks Trump did something bad, he just has no proof, and he has turned over as many rocks as he can.
This flies in the face of every prosecutor's job, and is actually contrary in every way to what they are supposed to do. The conclusion is either guilty or not guilty, or enough evidence is there to start some sort of proceeding. Since he did not say that he believes Trump to be guilty, that means he is not guilty, because it could not be proven in a court of law. This is how the whole justice system works.
Mueller is a coward to write this report in this manner... This is just another scandal to add to the 50 millions scandals we already have. He knew there was no collusion month's into Trumps Presidency, the rest of the time was spent waiting for Trump to try and obstruct justice.
This investigation, which is was not really an investigation if there was going to be no conclusion is a farce and a disgrace to everyone, US Government, it's citizens, Office of the Special Counsel, and ruined some good people's lives that wouldn't have been ruined if the investigation never existed. Whether you are republican or democrat, this report should leave you sick to your stomach.
I hear Flynn fired his attorneys, and is going another route, will appeal because of bad legal advice. We will see what happens.