Hi,
I found a gratis forum service provider for foss projects https://blog.discourse.org/2016/03/free ... -projects/ . Maybe you can save money and/or server administration work. There are scripts available for migrating content from phpbb. Discourse also has a nice feature called 'mail mode'. If the user activates it, it can use the forum like a mailing list. Maybe you like it. I just want to mention it.
Regards,
Andy