@AHg Disclaimer, I'm a drupal developer. Drupal is for "ambitious digital experiences" according to it's founder. It will certainly do what you need out of it but might not be on the easy side, it depends on what you mean by easy (plug and play?) and your experience with each of these platforms IMHO
I built two websites with Drupal 6/7, modules and a minimal custom theme / template some years ago.
Played with smf, phpbb and some more cms / forum software.
It's a small and private community (~30 users) to share photo albums with comment feature and a small forum (small talk, discussions).
Should work with mobiles (theme with custom colors, responsive).
Drupal with modules would be good / flexible / extendable, but maybe there is an simpler way for that small setup.
@AHg Well, for media Drupal 8 is much better but has changed a lot since version 6/7. I would say you should look for some specific software to do that, Drupal will be overkill for what you want to accomplish and probably hard to set up as you want. I don't know these other alternatives you mention but maybe try Humhub (more like social network) or ownCloud (more like cloud storage for media) ? Hope this helps :)
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