Would you prefer a stack that you know, or learn something new for a side project?

This is something I always get torn apart into. Sometimes I feel like I should really try a new language/framework. A nice way to learn something new.

But then I also feel like I should code it in a framework/language I use so that I can follow the idioms and best practices from day 1 and see what benefits it brings. Because you know that never happens in a production project.

I always want to learn from a side project. That being said, the thing I want to learn is not always a library, framework or language. Sometimes I want to get better at setting up a continuous deployment street.

My most recent project contains not a single new technology but instead I am attempting to create an encyclopedia that understands natural language. This should teach me how to operate nlp and predicate data models.