FARA, the foreign lobbying law, has seen an uptick in enforcement in large part due to the Mueller investigation, with ex-Trump aides Paul Manafort, Rick Gates and Michael Cohen all facing charges of failing to register as agents for work they did on behalf of foreign governments. A former lawyer on Mueller’s team, Brandon Van Grack, will lead a ramped-up effort to better enforce FARA. (Cohen has not pleaded guilty to FARA-related charges.)

The U.S. Attorney’s office in the District of Columbia also prosecuted W. Samuel Patten, who pleaded guilty to acting as an unregistered foreign agent in a case referred by Mueller’s office.

https://www.rollingstone.com/politics/politics-news/mueller-michael-cohen-810128/

In fact, it seems like Mueller's entire investigation stems from FARA violations. A Keystone, if you will. This article, though old, provides links to many of the known indictments.

https://www.politico.com/interactives/2018/interactive_mueller-indictments-russia-cohen-manafort/

I suspect only a few of FARA related indictments prepared over the last 2+ years have been revealed publicly (unsealed) so far.

Another Meuller-FARA reference:

https://www.vox.com/policy-and-politics/2018/2/20/17031772/mueller-indictments-grand-jury

https://www.washingtontimes.com/news/2018/oct/2/robert-mueller-probe-sheds-attorneys-brandon-van-g/

A former lawyer on Mueller’s team, Brandon Van Grack, will lead a ramped-up effort to better enforce FARA.