'BROWSER' is not recognized as an internal or external command,

There are two fixes i found that works perfectly well first one : install cross-env (npm package)npm install cross-env then you change your dev script to

"electron-dev": "concurrently \"cross-env BROWSER=none yarn start\" \"wait-on http://localhost:3000 && electron .\"",

please note that you also have to install concurrently if not already installed

second one : install concurrently and run this (on windows though)

"electron-dev": "concurrently \"SET BROWSER=none&&npm run start\" \"wait-on http://localhost:3000 && electron .\""