hi legey, looking at your package.json, i think you have quite a few things (dependencies and also commands) missing that are needed to build your project.
I only see this in your package.json:
"devDependencies": {},
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
which isn’t really enough. What commands are you running to build this app locally?
see this thread i responded to in depth today that contains a lot more info:
https://answers.netlify.com/t/react-app-page-not-found-error/21062
and this might be helpful too: