How to best manage pipelines with numerous Test Automation projects

We are attempting to set up our framework for Test Automation within our company.

What we envision is 5-10 “process” level repos (managed in Azure Dev Ops), and under each repo would be 20-100 test automation projects. Each test automation project would then contain anywhere from 1-50 test cases.

My question is, what is the most efficient way to set up pipelines for this structure?

We do not want a single pipeline at the repo level which publishes a new version for EVERY project under the repo whenever ANY update is made. We also do not want a pipeline for each individual project that ends up adding up to 100s of pipelines.

Maybe there is a way to design a repo level pipeline which can recognize which project is updated and ONLY publishes a new version of said project?

Thanks!