Here's a question I don't know the answer to. Petit jurors are instructed to avoid media relating to their cases and are often sequestered to avoid that and other external influences.
Grand jurors sit for longer periods than most petit jurors, and are charged with evaluating numerous cases, not just one. Therefore, it would be difficult and impractical to make any attempt to isolate them from media. So, I don't think they are, at all. But I don't know for sure.
As we have discussed In other context, details of criminal investigations before indictment are usually kept pretty quiet and a grand jury drops out of most cases post-indictment. So, in a general case, media exposure isn't that big a deal.
But it would surely seem that the media coverage of the first indictments and attendant shenanigans would make it very difficult to secure an indictment in any of these cases unless you were able somehow to assemble a purely pro-Trump grand jury.