Per the other poster, we don’t recommend ignoring TypeScript errors because it’s there to identify issues immediately before they turn into larger headaches.
That said, you can control how Appflow builds the app. It uses the build script defined in package.json (or there’s an alternative Appflow-only command). You’ll see the results of the npm run build command in the build log. So, this isn’t really an “Appflow concern” but rather relates to the web project and/or TypeScript configuration.
It looks like you can turn off error checking in the tsconfig file. See here.