Unfortunately it’s the distributors that add all the DRM protections to prevent piracy, but it makes it hard on the folks that are trying to utilize what they bought!
I haven’t tried importing since Amazon stopped the download of kindle books via the “usb” option if you have a kindle so I’m not sure anymore…
You can try epubor.com and see if that’s still a viable option. I know a lot of people here have used it in the past. I think there’s a free trial so you could see if you get lucky.
Otherwise you might want to investigate online bookstores in the target language country and see if they have epub versions of the books you’re interested in. I’ve done this for the past couple of German books I purchased as I knew the Amazon path was going to be “closed”. Ymmv depending on the target language.