The web front-ends multi-user clients I linked in this thread support file sharing, image uploading. For voice one could run either uMurmur or Murmur that also provides text and voice chat. People can be given permissions to create channels on Murmur whereas uMurmur you static define the channels as it is meant to run on home routers. There is a phone client for Murmur called Mumla. Murmur also supports file sharing but it was not really optimized for that to be used by a large number of people at once in my opinion. The voice quality of the OPUS codec is incredible. Open source video chat would likely be Jitsi and is a bit more complex.
These are not all-in-one solutions yet and certainly not as low-friction as most would prefer. I expect development to improve in all of these platforms as the centralized platforms go through growing pains and buy-outs.
Even then I would not expect everyone to migrate to these self hosted platforms and in a way I actually hope they do not or those platforms may get the unwanted attention from the powers that aim to protect us from our speech.
These are not all-in-one solutions yet and certainly not as low-friction as most would prefer. I expect development to improve in all of these platforms as the centralized platforms go through growing pains and buy-outs.
Even then I would not expect everyone to migrate to these self hosted platforms and in a way I actually hope they do not or those platforms may get the unwanted attention from the powers that aim to protect us from our speech.