You should check out Ladybird browser, it’s an impressive piece work, it’s definitely no ready for everyday use, but it is proof that a small community can develop and maintain a project as complex and large as a browser.

It is probably the only browser in active development that is not being paid by Google, even Firefox gets most of its income from defaulting the search engine to Google

Kotlin without a doubt.

Gives you more flexibility and freedom that most scripting languages. The syntax is clean and concise, the tooling is amazing and can compile to JVM, JS, Native and WASM.