You almost certainly will never do something novel while also learning a new language. And even beyond the learning phase: I've found that getting past this mental barrier of "whatever I build has to be useful" is essential to getting enjoyment out of side projects. Find it in yourself to enjoy the process for its own sake.

But it hasn't been done by you, in that language, right? Yoy are doing it mainly for learning.

Also, you will find you end up with a somewhat different feature set, get to fix what annoys you.

This is potentially a source of inspiration! Two simple options for example: your goal is to exactly reproduce the existing thing; or there are parts of it you don't like and want to improve on.

It doesn't really matter if it has already been done. It is actually good because then you can compare and try different things, or add the same features to learn how hard it is.

> What if anything I can come up with that aligns with my hobbies has already been done?

That depends on what your goal is. If your aim is to learn the programming language, code up that program/task/tool even if someone else has already done it.

Why is it relevant if it's already been done?