It's just the cost of doing business with some control. Get a cheap domain and a low-end VPS/VM with a fixed IP (Vultr, DO, Hetzner). You can't really expect to get everything free.
You can host a simple forum on a RaspberryPi, you can stack a few of them together for better performance.
Just food for thought.
need to pay $$ for static IP address
$20/y should be enough. That is a lot for some people though. But for a business it should be no big deal.