This! Porting a small application that you already know well to a new language or stack is an excellent excercise. But IMO it's also useful to read some introductionary texts and existing code on the target platform while doing that to see if there's some useful idioms and practices you can benefit from - especially if the languages follow the same paradigm. There's quite little use in just writing the existing code in a new syntax.
I make the same project every time I pick up a new language.
It lets me pick up the differences quickly, when all the logic basically stays the same.