Only the people that admit Durham interviewed them.
"As the two spoke, Solomon made reference to the fact that U.S. Attorney John Durham has been subpoenaing witnesses and that several have already appeared before the grand jury. (It was reported recently that Durham had driven down to Washington, D.C. in March because the investigation was ongoing, but there had been no reference to what specifically was the reason for his trip.)
Solomon said, “I’ve seen some evidence of the grand jury work [Durham’s] in the last four, five, six weeks. It’s been going on in the middle of the pandemic. And I think we’re going to get a better sense of what that looks like…”
https://www.redstate.com/elizabeth-vaughn/2020/04/12/solomon-durham-has-subpoenaed-questioned-witnesses-before-a-d.c.-grand-jury/
"A new question about the mysterious Maltese professor Joseph Mifsud is: What did he say on a taped deposition handed to the team of special Justice Department investigator John Durham?"
https://www.washingtontimes.com/news/2019/oct/27/joseph-mifsud-gave-deposition-john-durham-russia-g/
Bad News For Coup Crew – Former NSA Director Mike Rogers Working With John Durham For Several Months…
"Merry Christmas. The intercept is reporting that former NSA Director, Admiral Mike Rogers, has been working with U.S. Attorney John Durham for several months during his investigation into the origin of the 2016 intelligence operation against candidate Trump."
https://theconservativetreehouse.com/2019/12/20/bad-news-for-coup-crew-former-nsa-director-mike-rogers-working-with-john-durham-for-several-months/