What framework does an app like Evernote or Notion use

Does anyone know how apps like evernote or notion are made or at least what frameworks they might use? I was wondering what the web version would use, but any info on the desktop or mobile is also appreciated. Do you think they use their own servers or they use something like AWS for data storage? I have taken many online courses that taught me Node.JS and various javascript libraries like React, but it got me wondering if big companies also use things like React or their own proprietary libraries.