Thank you for your response!
My forum is indeed recent—it’s only been live for a couple of weeks, and I haven’t migrated it from any other platform or domain. I’m using Discourse from the start.
I’ll definitely look into adding the structured data markup as you suggested. Do you think this could also be tied to how Google initially indexed the site? Or is it more likely related to metadata that might unintentionally mention “Instagram”?
Thanks again for your help!