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I think (but I have not tested) that if you can use the DeDRM plugins to import your books into Calibre... You might be able to use Calibre's conversion function to make them all ePubs (which are Kobo friendly). I don't have a Kindle but I do use a Kobo and have had to run DeDRM and some conversions to make books compatible.
Good luck!
This works for me. So long as you have a Kindle device registered on Amazon, you should be able to download directly to a desktop. The DeDRM plugin mentioned removes the DRM during ingestion into Calibre and requires an actual token from Amazon which is linked to the Kindle device you downloaded from.
I use this to get Amazon eBooks into my Remarkable 2 which requires DRM free.
Yeah, +1 for Calibre amd DeDrm, recently I needed to jump through some more hoops since Amazon stopped delivering to that old Kindle Desktop version for PC and needed to use the Android version but generally works pretty well. I'm also surpised how many of the books I read actually don't have DRM at all but that is obviously down to my obscure taste (mostly indie SFF).
If all else fails I just buy the book with DRM and then pirate it from the high seas, no harm done (except for the harm supporting big platforms like Amazon does 🤷♀️).
I have a Kobo Clara HD, also moved quite a few years ago from a Kindle to this. I really love the accessibility of the Kobo ecosystem. The store, while not as vast as Amazon, has good books to choose from. You can also load your own items onto it. Calibre has good support. All in all, I am happier with it than the Kindle; not worried about a book disappearing on me.