SMF 2.1 is under active development at Github (https://github.com/SimpleMachines/SMF2.1)
Before you request for support or maybe report a bug (http://www.simplemachines.org/community/index.php?board=137.0), make sure you have fetched the latest code from Github.
Please keep in mind that the releases you find at our downloads page are the state of the code when said release was... released ;D On Github you can always get the completely up-to-date code and, who knows, maybe the problem you are having was even fixed already? ;)
As always, keep in mind that Beta Releases are NOT recommended for production sites.
If you are reporting a bug/issue related to new responsive parts, please include following details;
- Device name (example: Lumia 520)
- Resolution (example: 480x800)
- Screen Size (example: 4'')
- Browser (example: Internet Explorer -with version if possible-)
- Software Version (Windows Phone 8.1 GDR 1)
- Screenshot(s).
If you are not sure about the details of your device you can skip them but its important that you should supply device name with browser.