Best practices and guide for network programming

I've read through the official unity networking multiple times and still feel quite nebulous in regards to how to best structure and approach network programming. I realize it depends a lot on the architecture as well. Seeing the depreciation of HLAPI and LLAPI has made me hesitant to keep pushing forward with that paradigm. Are there paradigms that can be learned that are applicable regardless of what programming language ? What is a good resource to deep dive on network programming theory and design patterns? What paradigms would make the most sense with the direction that unity is moving in with ECS ? Thanks for any insight!