Electron uses Blink as a renderer which is LGPL. Everyone who ships an Electron app has to apply to the LGPL terms in the exact same way than for Qt. It's just the Electron API itself which is MIT. If I'm not mistaken, Electron also ships with FFMPEG which is also LGPL.

Source: the copyright headers here: https://chromium.googlesource.com/chromium/blink/+/refs/head...