The idea of a simpler, less bloated Slack is definitely appealing to me as a user, but I'm not sure there's much of a market. What kind of companies are they targeting here? Small enough that user access dialog is usable and the lack of features/integrations is acceptable, but also willing to pay $300 and take on the trouble of self-hosting.

My biggest issue is with the UI though. Without watching the video I wouldn't know what half the buttons do. Many of them have multiple actions/states and there are no labels or tooltips for buttons.

Forms do have labels, but you have to click an icon to read them. It seems the only benefit of this is that you can also see what the label is in French, but unless you're translating the app, most users would prefer to just see the label in the language of their choice. And there are some dialogs where just English text is shown, so this isn't entirely consistent. Maybe I'm totally missing something here, but I think simply having a user select their preferred language isn't something that needed to be innovated away.