The upgrade in phpBB left the Smartfeed plug-in behind. I raised it with the developer and he sent me a fix which is now working. Except you have to generate a new URL to replace the old but its well worth the trouble.
You can generate a Smartfeed URL for Atom/RSS reader from the Smartfeed link on the top menu. I use Aggregator on Android as a reader. There are many others available for every known platform so you can see all the customise a list of all the latests posts on most forums and blogs.
Stuart