Gitlab, many other lesser known alternatives (such as the aforementioned sourcehut, although that has a different paradigm than github)
> Typescript
Facebook's flow is probably the closest. There's also dart, and many, many other languages that can compile to JavaScript.
> npm
Yarn is the obvious one (although it still uses the npm repo). Or you could leave node altogether and use deno. There are probably other alternatives.
> Visual Studio Code
(Neo)vim and emacs are both good options, although they have a steep learning curve. There's sublime text if you don't mind something proprietary. Probably others I'm less familiar with.