Since May 25th, 2018, there are a lot of expectations and discussions, on what is
GDPR (The General Data Protection Regulation) and how forums could be made compatible with it.
But the only thing you need to know about it, is how you deal with a person's identifying information. This information should be kept safe and not disclosed publicly unless a personal permission is given.
It's quite easy to make miniBB compliant with such rules, because none of its scripts are designed to collect a personal information or identify a person. As you know, since its first version it allows anonymous posting even without prior registration, and today it's probably one of a few forum software which still allows this. Yes, it collects IP addresses like
any website does, but they are not used to identify anyone personally; and actually -
how could be they used, if you may be behind VPN or private browser or whatever... IP addresses are only used for digital sessions (like in Who's Online add-on), login/authorization, some way could be used to prevent spam, in the
Polls add-on, they are used to track a guest vote.
Generally speaking, you don't have to make something special to your miniBB forum to make it compliant with GDPR, because it's already compliant.
But you if you are still worried, you could use the updated
Disclaimer & Policy add-on and/or add it to your forum prior to Registration, or as a standalone Privacy page to make it clear how your forum uses cookies and keeps the registered data. You also could
test and check it straight.
Of course, you are free to edit any part of it and add new paragraphs; and you are
welcome to add your comments or suggestions here in this thread, or in the
add-on thread.
Just to repeat: GDPR is about dealing with information, which publicly identifies a certain person. Unless your forum is about opinions and not about real persons, you should not have a big headache about it. Also, this Regulation takes place only in the European Union. Unless your data is kept outside of EU, it's not your obligation at all.