I also struggled with setting up Strapi with TypeScript in a monorepo. To help, I created a starter template that combines Strapi, TypeScript, and Next.js with Turborepo (a monorepo solution from Vercel). It might be just what you’re looking for! 
Check it out here: GitHub - sawden/turbostrapi: 
TurboStrapi: The fast lane to kickstarting Strapi & Next.js projects.