I usually learn by...
So I guess I'll usually learn/practice by using it 😉.
Especially if you can't practice it at work or don't have a side project that fits, I'd strongly recommend contributing to OSS that uses the language/framework. This way, you often even get reviews of your code for free.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.