Hi @maya-morin ,

The wpForo is a WordPress forum plugin that integrates with the WordPress user system. It leverages the user authentication and management system provided by WordPress. This means that when you install and use wpForo on your WordPress website, it will work with the existing WordPress user accounts and user roles.

@maya-morin if you want to keep your forum users separate from your main site WordPress users, there's only one way to do this. You could install WPForo on a totally different WordPress installation under the same domain. For instance:

https://domain.com (Server1)

https://forum.domain.com (Server2)

You can then link your sites using top menus items or links etc. However, keep in mind this would be a totally different site even though the domain could be the same, Admins from your main site would have no access to the forum etc. You would need to create separate Admin accounts on the WPForo site etc. 

You could then block/hide registrations on your main site, effectively forcing everyone to register on your forum site. 

Your secondary WordPress installation in the subdomain would be the one carrying out the forum user base.

Maybe this is a solution for what you seem to be looking for, but it's complicated and maybe not an ideal solution.