Last week I was testing Turborepo (acquired by Vercel few weeks ago), and how to integrate with Netlify. So, I created a repository that has two NextJS apps (with netlify.toml) file. At README, you can see how to configure many apps into a monorepo and deploy to Netlify.

https://github.com/raisiqueira/turbo-netlify

For more details, see the Netlify documentation about how to deploy monorepo apps: https://docs.netlify.com/configure-builds/common-configurations/monorepos/#build-multiple-sites-from-a-monorepo

Next steps are integrated the Turborepo remote cache at Netlify and perform a better deployment pipeline for frontend apps.