Slack is mandatory in my team, sadly. I must say that they have a good native linux client, so I don't mind having it on my work machine. It stays out of the way, doesn't try to be intrusive etc. I don't like subscription services, but their attention to linux users made me not discard their software off hand.
Dropbox is another story. A steaming pile of linux-unfriendly horse-manure. They support apple though. Nuts.
#slack #dropbox #linux #ClosedSource #software #LinuxFriendly