Alternatives

After doing some research there are quite a lot of players in the file upload widget space.

https://www.filestack.com/
as well as all of these https://www.producthunt.com/products/filestack/alternatives

https://www.uploader.win/
https://uppy.io/
Kind of https://www.producthunt.com/products/shubox

Uppy.io seems to be open source and easy to use in your project as a library.