I used a Kindle for a decade, but then switched to a Kobo device (Libra 2) and I really enjoy it. Kobo is friendly to users modding the device, so you can easily install KOReader that is a superior interface if you read a lot of PDFs.

In spite of being an avid reader, I have never actually bought an ebook. All my reading comes from LibGen, Anna’s Archive, or their predecessor communities for free downloads. Consequently, I never suffered from Amazon’s ecosystem: as soon as I took any new Kindle out of the box, I put it in airplane mode and only sideloaded books over USB.

Perhaps not precisely what you’re asking, but there are simple ways to download the Kindle books that you paid good money for, and decrypt them to plain ePub or PDF using Calibre.

I was a kindle user and recently switched to Pocketbook. I’ve been buying new ebooks from ebooks.com which are often already drm free. For me, there haven’t been any downsides.

There are some options where you can buy DRM free ebooks listed at https://www.defectivebydesign.org/guide/ebooks