When I narrate an audiobook partly or totally for royalties, I usually get free review copies from Audible. They are for Audible only, not other platforms.
Specifically, they are for Audible US and Audible UK.
You can access those Audible storefronts from other regions by changing the location settings on the Audible phone app or a location override link on the website.
I'd love copies for more platforms & regions but it's out of my hands. (Talk to the behemoths!)
Audiobook reviews make a big difference for boosting sales. They signal to the platforms that people like the books, and the platform algorithms then boost the visibility.
Reviews that are specific about what a listener liked and why can also encourage like-minded shoppers to buy the books.
Reviews go a long way to helping me and the lovely indie authors I narrate for.