This frustrates me a lot too. Whenever I encounter non-crossplatform Electron apps, I extract the mac or windows app.asar files and so far, all of them have ran fine on Ubuntu. That means it's just a matter of not taking the effort to package the app for multiple platforms. I get that packaging is not the most exciting part of application building, but it's not rocket science either.

If anyone has an Electron app and wants/needs help with cross-platform packaging, feel free to contact me.