1. Learn Electron and implement an app, publish to all platforms.
2. Choose your target OS, learn the native toolkit, implement the app, switch to other OS, implement again, rinse and repeat for all, and in the case of linux you have to deal with multiple toolkits and you have to know the quirks around Wayland support (with electron you don't necessarily as chromium handles most of that).
One of them simply takes way more time and effort than the other.