Since when you need a web browser to display content?
Slack could easily use native widgets, without embedding any HTML.
Slack could easily use native widgets, without embedding any HTML.
For instance GTK apps in the earlies 2000s were easily displaying content as rich.
Point is, native or not native, this should not matter for a well optimized code. We are not talking about a AAA game here, it's just a chat app. It should not be burning cycles when inactive.
Rich interface doesn't mean HTML and CSS. Have you seen good iOS apps? Their interface is just as rich and yet it's pure Swift/Objective-C compiled down to native code.