Translation:Tomorrow, of course, everybody will know about this.
"Of course, everyone will know about this tomorrow" is also rejected. Is there any good reason it should be? From an English language perspective, the Russian word order is so fractured there's at least a half dozen ways to order the English translation and no clear way to say which is closest. Just for starters, "Of course," "Tomorrow," and "Everyone will..." are all valid beginnings, and there are at least three different places in the sentence "of course" can go.
Although this difference is sometimes lost in print, "everything"-"всё" (different last letter). As for your question, the translation would be different depending on whether you use "they" to describe specific people or as a "filler" for unspecified subjects.
In the former case: "Завтра об этом, конечно, они будут знать всё" or "Завтра об этом они, конечно, будут знать всё".
In the latter case, you would actually employ a passive construction:
"Завтра об этом, конечно, будeт известно всё" - "Tomorrow, of course, everything will be known".