Not sure about two Android phones, but Signal does exactly that. I use the same account on three different devices. Two desktop and one phone. It has a note-to-self feature that allows you to upload up to 100MB file.

My overall favourite app replacing the Kindle app. It is available on almost all platforms. Fully open source and free.

https://readest.com/

Jumped to Bazzite never looked back. Let’s goooo