How to filter subdomain traffic from GA4 results

I just recently made the move to Google Analytics v4.

My site has a blog on the TLD and a forum within a subdomain. The problem is the subdomain gets a significantly higher amount of traffic than the blog so when I'm trying to view results for the blog it gets skewed by forum results.

How can I filter out the subdomain? I don't see it as a condition or "dimension" in the filtering options.

Thanks in advance!