It probably doesn’t matter at the scale you’ll be operating. But Backblaze has more data than anyone here about reliability.

https://www.backblaze.com/blog/backblaze-drive-stats-for-q3-2024/

SimpleX is pretty good for person to person chat I’ve heard it doesn’t handle large groups very well though.

Mattermost is an easily hostable slack-like option.

First project created, only want $50k, delivery is basically as soon as the project ends.

I would be surprised if the backers of this project receive anything.