Can anyone advise where / how to get a copy of Kindle for Mac 126.1? I just updated my MacBook from El Capitan to Big Sur and am struggling to get everything working with Calibre, tools, etc. I think I have most of it together thanks for posts on various forums here, but need this last piece. Any help greatly appreciated.
You do not need KindleforMac because you have a Kindle Oasis. You can use the Download and Transfer via USB feature on Amazon in the Manage You Content and Devices section.
Okay, will try that. I thought that only worked with older kindles. I confess to finding this somewhat confusing. Thanks.
Any version for Kindle4mac can be found here:

https://mac.filehorse.com/download-kindle-for-mac/old-versions/
How do we know these are legit? Does anyone have a way to validate these?
For selected versions you can verify them by following the instructions under the heading "Obtaining and verifying Kindle for PC/Mac software" in this post.
Thanks for the info - much appreciated.