Please help to deploy nextjs project alongside another project (library) in same repo

[zoultrex]

My repo initially had only 1 project, and this project started from the next-redux template, fully integrated with vercel meaning that I only had to type vercel on the CLI and the build was a success by using all default configs.
This nextjs project is my web app, its the one that serves the frontend and one API route.

Now I have added another project into the same repo, this second project is just a library, but its a project on its own, with its own dependencies. My nextjs web app now uses a few libraries from this second project.

The only way I was able to make it all build was by overriding the build command and using a sh script, just like this tutorial shows: https://www.storyblok.com/tp/different-build-commands-branch-name-vercel

The problem now is that when I access the vercel deployment link, I get a 404

I was only able to make it all build when I changed the framework preset to other (as you can see on the image above) on the build settings on vercel control panel.
Doing so makes it all build but I get a 404. If I put the framework preset back to nextjs, the custom build fails.

As per the tutorial - my vercel.sh script is super simple:

cd second-project
yarn
cd ..
next build

I guess what I'm missing is configuring manually the way the nextjs framework preset was deploying the nextjs project and setting the index page correctly so i don't get a 404. But how do I achieve this?

Better question than that may be: would that be the best approach? I have the impression this is over complicating things.
I would love to be able to just run 1 command before the entire default build settings, which would build my second project dependencies and then continue to build nextjs project with default configs. Would that be possible/easier?

[zoultrex]

Some more info
Comparing the logs from previous builds that were successful (when I only had the nextjs project alone on the repo) to this build returning 404 I see two lines missing on this new build with the issue

See the two lines in between asterisk

Done in 13.53s.
**
Traced Next.js server files in: 318.341ms
Created all serverless functions in: 535.508ms
**
Uploading build outputs...
Deploying build outputs...
Build completed. Populating build cache...
Uploading build cache [62.39 MB]...
Build cache uploaded: 2.047s
Done with "package.json"

[zoultrex]

I wonder if someone can comment out if this actually possible, otherwise I'd look for another solution

[zoultrex]

After some tests and some research I found two things

1. I since the nextjs project is on the root of my repo (obviously alongside with its package.json) I tested copying all the node modules dependencies from the other project, into the package.json for the nextjs project and it worked.
   So apparently for this to work all the modules must be installed in this specific way.
   I'll use this workaround for now, although obviously not ideal

2. decided to look for some kind of library that will help me handle this task
   Quite a few people have recommended turborepo and thats the one I'll give a shot first, but wont update here since it will be out of scope

Now I gotta say I'm a bit disappointed with vercel team support here on github.
This issue was opened for 9 days and there was no tip, no suggestion, no question to further get info to help me out at all.

Worse even, turborepo is now a product owned by vercel, acquired last December.
Someone could have dropped two words that would have saved me quite some time :" try turborepo"