Hello,
I have noticed a design issue with Flarum. When you create a post, you also create a title for it, if you look at the source of Flarum for a post, you will find the exact same <title> and <description> tags on all the posts. This will cause a massive issue with search engines as each page(for Seo and better indexing) should have its own title and description. For the title you should limit its length to 60 characters while for the description try 300 character due to this latest update:
https://www.compose.agency/insights/meta-description-length-2018