Support for this mod is provided in the Simple mod Rewrite forum.
Release thread : phpBB SEO Simple mod Rewrite V 0.2.4.

index.php?c=xx => catxx.html

viewforum.php?t=xx => forumxx.html

viewforum.php?t=xx&start=xx => forumxx-yy.html

viewtopic.php?t=xx => topicxx.html

viewtopic.php?t=xx&start=xx => topicxx-yy.html

viewtopic.php?p=xx => postxx.html

profile.php?mode=viewprofile&u=xx => memberxx.html

Even though the simple mod rewrite does not inject titles in phpBB's URL, it's possible that you will
Install a patch for a module which uses titles injection.
The following would apply to possible the title injection performed by eventual patches on phpBB modules such as smartor album.
In case you're only using phpBB, you can safely ignore this part.
Just know the mod is able to deal with many char-sets in case there is some title injection.

This version supports all the char-sets supported by htmlentities().
For all these char-set, the mod rewrite will only inject the possible ASCII Chars, after removing all accents, available in the titles.

For example : "نرم افزار - Software" will be formated prior to injection in the following way : "software".
Please read the phpBB SEO Simple mod Rewrite V 0.2.4 for more details.

If you are migration, eg if your forum is already indexed using different URLs, you'll have to use another robots.txt and install the zero duplicate.
The migrating procedure will allow you to migrate and keep your previously indexed pages. Older links will be HTTP 301 redirected to the new ones. It is rather simple, but the solution depends on cases.
Let's meet in the migration Simple mod Rewrite forum.