Specifically in the context of k8s and docker which file extension is preferred?

When I asked my friend, his response was quite convincing...

I like .yml, it's 25% faster to write

☝😆

Personally, I'm fine with whichever is the "standard"/majority preference for consistency sake.

Fun fact - Though .yaml is recommended, many codebases and documentation around the 🌎 begs to differ.