Just developed a new extension that works after the 1.27 changes that crippled the old one. I now use the Extension:Auth_remoteuser extension, which handles the logging in and have added a very simple amount of code that checks for a phpBB session and logs them into MediaWiki! It is quite easy now thanks to that extension (also the same extension that phpBBSSO was originally based upon).
You can download the code from Github, or install with composer.
https://github.com/multidimension-al/phpbbauth
This was tested using MW 1.30+ and phpBB 3.2+. Works great as far as I can see!