Hmm Yamimono, I’m not sure what you mean by that. Their app is cross-platform, and their mobile app is top tier. I don’t use tablets so I can’t speak to that, although if you had an issue for Discord on Tablet I’d expect similar for Slack.
As for Nitro, the only thing you get is the ability to use global emotes from different servers, larger file upload sizes, and higher quality screen sharing. Most things you get for free at Discord you would have to pay for at Slack, like history saving for chats, call and screenshare, more permissions, etc.