I track a lot of COSS projects and I wouldn't say most of them use those languages.
For interactivity, JavaScript is almost unavoidable on the frontend so it is understandable that teams use TypeScript (that gets transpiled into JS) on the frontend, but I would be hesitant to say most projects use TypeScript or Rust on the backend.
I know of several COSS projects that are written in Java, Python, Golang, C++. These are language that are not yet represented by Algora so there is plenty of room for you (or a competitor) to grow the pie of paid contributions to the COSS landscape.
For interactivity, JavaScript is almost unavoidable on the frontend so it is understandable that teams use TypeScript (that gets transpiled into JS) on the frontend, but I would be hesitant to say most projects use TypeScript or Rust on the backend.
I know of several COSS projects that are written in Java, Python, Golang, C++. These are language that are not yet represented by Algora so there is plenty of room for you (or a competitor) to grow the pie of paid contributions to the COSS landscape.