The conclusion: "Many authors point to the Internet in general and social media in particular as possible drivers of political polarization. We find that polarization has increased the most among the groups least likely to use the Internet and social media. Under appropriate assumptions, these facts can be shown to imply a limited role for the Internet and social media in explaining the recent rise in measured political polarization."
If you want to go further down this rabbit hole, I'd recommend "Why We're Polarized" by Ezra Klein. It acts as a synthesis for a bunch of work just like this.
also on polarization: https://www.pnas.org/content/114/40/10612
The conclusion: "Many authors point to the Internet in general and social media in particular as possible drivers of political polarization. We find that polarization has increased the most among the groups least likely to use the Internet and social media. Under appropriate assumptions, these facts can be shown to imply a limited role for the Internet and social media in explaining the recent rise in measured political polarization."