To obtain un- redacted Meuller report, Congress may have to initiate impeachment proceedings

Existing legal precedents have declared that Congress can only have access to Grand Jury material (known as Rule 6e) in the performance of their duties of impeachment, which in these rulings, was also considered a "judicial proceeding":

https://www.justsecurity.org/44191/mueller-grand-jury-report-public-hand-congress/

When the Eleventh Circuit later considered whether the grand jury materials could be provided to the House Judiciary Committee, the parties then agreed that impeachment was a “judicial proceeding” within the meaning of Rule 6(e) and that therefore a court could order disclosure under the terms of that Rule. The Eleventh Circuit found that disclosure to the Judiciary Committee was warranted for essentially the same reasons it allowed disclosure to the Investigating Committee. The court found, however, that it could not order the Judiciary Committee to maintain confidentiality, as this would impinge on Congress’s constitutional authorities, and noted that while the Committee said that confidentiality rules would apply to the documents, the Committee was free to change its mind and make them public. In re Request for Access to Grand Jury Materials Grand Jury No. 81-1, Miami, 833 F2d 1438 (11th Cir. 1987). In sum, therefore, the Eleventh Circuit suggested two separate legal bases to order disclosure of grand jury materials to a congressional body considering impeachment, relying either on the court’s inherent authority or on the “judicial proceeding” exception of Rule 6(e). And the Eleventh Circuit recognized that the Congress may subsequently choose to make that material public.

These precedents strongly indicate, therefore, that Congress would have no difficulty subpoenaing the results of Mueller’s grand jury investigation should that inquiry end without an indictment of Trump, but with some indication that impeachment might nonetheless be warranted. (The same would be true for other executive branch officials if Congress believed that the grand jury materials could assist in the consideration of their impeachment). And this result would make perfect sense. Although grand jury secrecy serves important interests, and generally restricts the use of powerful investigative tools to a determination only of whether crimes have been committed, where the question of impeachment is on the table, the interests tilt toward disclosure. Particularly if one concludes that Trump cannot be criminally indicted (because that avenue is constitutionally barred for a sitting President) and that the only recourse is impeachment if he has committed crimes or serious misconduct, it would plainly be in the public interest for Congress to have access to all available evidence when considering the grave question of impeachment. Of course, Congress could use its own subpoena powers to reproduce Mueller’s investigation and collect all the evidence itself, but this would result in months if not years of delay for no identifiable reason. What if Congress wanted the grand jury information but not tied to any real prospect or stated interest in impeachment? It is an open question whether the societal interest in a particular Congressional investigation would also inspire courts to allow grand jury information to be handed over. Some of the existing cases that we have discussed appear to hinge on the connection to an impeachment proceeding or the prospect of impeachment.

The same site also makes a case for the use of "Presentment" as a way to indicate a president has committed a crime without indicting him:

https://www.justsecurity.org/44252/untold-option-mueller-grand-jury-presentment-alternative-indicting-trump/