Hello.
Hope everyone is fine. :)

I don't think I've ever seen someone mention it here on GOG forums but there's a Linux client to download your Amazon Prime games.

It's called 'Nile Project'.

Unfortunately, many games that Amazon gives away through its Prime subscrition are tied to their Windows launcher, but almost all of the games they give away are DRM-Free and can be safely downloaded, installed, played and stored without problems.

Here's its github link:

https://github.com/imLinguin/nile

Take care.