So, coming back 2 days later to tell that I could solve the problem.
The problem with the InternalBytecode.js file normally lies on some dependency error.
I solve the problem going back into the last commits I've done, till one of them didn't had the problem.
It ends up that the most helpful message had nothing to do with this InternalBytecode.js file, but with the first message I wrote on the question: "ERROR Warning: TypeError: Cannot read property 'regular' of undefined"
As expected, it was a TypeError, where a obj field (fonts) was set to "any" instead of "never".
export const lightTheme: Theme & NavigationTheme = {
dark: false,
colors: {
...
},
fonts: {} as never,
};
So, if you find yourself stuck in the same problem, try to look for the first log and interpret it, it might on the most of the cases be a type problem.