I would second Elixir. Either that or Rust. Sure both are popular, but for good reason.

They are completely different from the languages you use.

You will be introduced to new paradigms.

As a person who used the same stack as you (albeit typescript instead of JavaScript), I think it would be a waste of time to learn C#. It is so close to Java, and learning it may make you hate having to use Java, because it seems a bit better put together. Even though it runs on Linux, and is a good language, I don’t think there is ever a reason to chose it over Java, because M$.

Manjaro Gnome worked with my Lenovo T480s out of the box.

I’ll have to check out this book. Just remember HTML cannot be parsed with regex

I saw something similar to this on an intel Mac running canary years back. I believe toggling GPU acceleration in the settings resolved the issue.