Trying to create a user forum on a SharePoint Online site

fred_valaris if a Yammer community wasn't suitable (which it probably would be) what I would probably do in this scenario is to have a form on your SharePoint site that saves the response to a list in SharePoint via a flow in Power Automate. You would create a view of the list and format that view with JSON to make a nice-looking forum-type section on the page. I've done this one one of my sites for a suggestions forum-type situation. 

Come back to me if this looks like what you want and you need the detailed flow steps and the JSON code. But you'll see we are also using a Yammer community.

Edit: Steven Andrews the discussion board can't be used in the modern experience, so Yammer or my solution above with a form, flow and list are the available - and very good - options.

Rob
Los Gallardos
Microsoft Power Automate Community Super User