Python (especially focused on AI and data analysis) and Javascript/Typescript are where most of the activity and interesting jobs are right now. These are also fairly easy languages to become competent in (though JS obviously has some idiosyncrasies to learn).

Go is also extremely popular right now for the interesting work that requires better performance (blockchain, network services, etc.).

C# and Java (and more recently Kotlin replacing Java) are still extremely prominent in large companies.

Mobile is kind of all over the place. Java/Kotlin on Android and Swift on iOS are the native languages of each platform, but React Native (JS using a bridge to send messages to the native side), Flutter (Dart language, using Skia to render it own controls instead of native controls), Xamarin/Maui (C# wrapping native controls), and webview solutions like Capacitor are all somewhat common. Mobile is a little harder to break into.

Lower level languages like C, C++ and Rust are all very prevalent in domains like blockchain, anything that interacts with hardware, and a number of other domains.

SQL, R, Python (already mentioned) are very popular in data analytics. If you are working with data at all, even databases for your application, at least get familiar with SQL (Postgres, MySQL, SQL Server are the big 3 database engines).

Anything outside of those mentioned above are going to be more niche, and not likely to have jobs available or open source projects to work with.