cilia No extension is going to make your forum rank better in Google. You will need to work on content, internal and external linking profile, and web speed. Extensions like this help Google understand your site better, but they don't make it rank.
Encourage your users to create quality content that helps other users. Otherwise, Google will understand that the content on your site does not add value.
I am a professional SEO, and I bet on Flarum because of how it is built. It is far away from the conventional forum scheme, which makes conversations flow and there is always movement. In addition, its loading speed and responsiveness are exceptional (maybe a lot of JS, but Google understands it well).