Take a good look around and check how often people do really change computer platform. And you already have so many things that are different that the "same look" is just an excuse. Gnome, KDE, macOS, Windows does not have the same UX in their file explorer which is a basic utility that everyone has to use. Same with connecting to a WiFi and creating a new user account.

So why would you want Discord to be consistent, when you're mostly using the same desktop (or switch between at most two) for hours.

The thing is when HIG were followed instead of everyone trying to create their "brand", everyone knows where the common actions were. You learned the platform and then can use any app. With the new trend, you would only have one computer, but any new app is a new puzzle to figure out.

The best way I’ve seen this implemented is having the domain be a library or a protocol/server. For a lot of saas, we already have people writing the mobile versions and the web version..

Yes. It’s more work than dumping Electron on users. Quality often is.