I'm sharing this article because (despite being Americentric) it focuses on third-party election interference, not just in the US, but in other nations too, and challenges some common assertions:
"The findings challenge some common claims about FIEs. Only 15 percent of the FIEs included efforts to polarize people in targeted countries (defined as pushing on both sides of one or more political issues; for example, promoting both pro- and anti-gun control content). Other tactics were more common: About 65 percent of the efforts worked to defame specific individuals."
"Twitter and Facebook were by far the most popular platforms for these kinds of coordinated inauthentic behaviors. Of the cases we identified, about 83 percent used Twitter as a tool, while about 50 percent used Facebook."
https://www.lawfareblog.com/managing-and-mitigating-foreign-election-interference