Most electron projects exist because engineering organizations couldn't afford to hire platform specialists for every platform they want to run on.
But most frameworks don't come even close to CSS and all the possibilities to create custom controls. It often requires to build everything from scratch in code, which is really hard for more complex layouts.
Also things like accessibility. It's quite easy to make web ui accessible, much harder to do it with custom native control.
Show me a few web apps that are "really good" with this, and don't achieve it by making 30%+ of the screen be spacing.
We developed on Windows NT and deployed onto HP/UX and Solaris.