Beta Big Sur kindle problems.
Le service client d'amazon n'a pas pu faire grand chose pour moi : il m'a demandé de supprimer l'application et de réinstaller l'application plusieurs fois mais le résultat est le même. Kindle est inutilisable pour l'instant ce qui est un problème.
So I've run into this same issue, where the Kinder Reader App is extremely slow. I cannot zoom and focus on a page without taking 30 seconds to deal with the lag.
I'm almost sure this is an issue from Apple requiring (forcing) the move from OpenGL, to Metal. I say this, because any app not using Metal experienced a huge slow-down after the update (due to the limited OpenGL core). Looking at the version history of the Reader app, that seems to be the case as there are no mentions of any framework updates since El Capitan.
Anyways...
The only resolve I've found is to stop using the official MacOS app. I often use to iOS reader anyways, but when I want to use the laptop, the Kindle Cloud Reader works well, even though it's limited in the feature department. 😞 https://read.amazon.com/
We can only hope that Amazon updates the app in the near future. 🤞