The BuddyBoss App is compatible with a multi-site environment. Some of the branding options are available for each subsite such as the color, home screen logo, tab bar menus, etc. You can also set each subsite page to each subsite interface on the app. In a multisite environment, all sites share the same user profiles. Your users will be able to switch to other subsites on the App and will be able to view the content of the selected community.
With that being said, you cannot create a user for a specific community or restrict user access to a sub-site. This happens because a multi-site has a shared database.