My answer, not much.

NOTE:  On Obstruction of Justice Mueller wrote, “Because we determined not to make a traditional prosecutorial judgment, we did not Draw Ultimate Conclusions about the President’s conduct.”

He could have wrote, “Because we determined not to make a traditional prosecutorial judgment, we did not draw ultimate conclusions about the President’s conduct.  Therefore it is up to Congress to make this decision," and we would not be in this mess.

"With Mueller testimony, can Democrats expect a ‘breakthrough moment’?" PBS NewsHour 6/26/2019

Excerpt

SUMMARY:  The debate over the Mueller Report and its political fallout continue.  More than three months after the investigation concluded, the former special counsel himself will testify before two congressional committees on July 17.  Yamiche Alcindor joins Judy Woodruff to discuss the format of the appearances, why Democrats are hoping for a “breakthrough moment” and what Mueller won’t be able to discuss.