Can I deploy a locally built Next.js app to Vercel?
The vercel build command can be used to build a project locally or in your own CI environment. Build artifacts are placed into the .vercel/output directory according to the Build Output API. When used in conjunction with the vercel deploy --prebuilt command, this allows a Vercel Deployment to be created without sharing the Project's source code with Vercel.
https://vercel.com/support/articles/deploying-locally-built-nextjs
