luceos this is known and not solved
This is solved and isn't an issue with Flarum but a nginx/Apache configuration error. Two urls should never have duplicate content. So www.domain.tld/page.html and domain.tld/page.html should not ever yield the same content. Having it set up like that causes SEO issues, inconsistant urls, and other issues. The common standard is to redirect domain.tld to www.domain.tld but it's becoming more common to redirect www.domain.tld to domain.tld. All in all, when using a root domain, it is absolutely esstential to redirect one to the other. I'm glad such an obvious problem like this happens with Flarum which can help avoid less obvious and common errors in running a website.