Is there a non-DRM format + an e-reader combo that allows for bookmarks, text selection, dictionary search? Ideally I would prefer to keep my Kindle but would really love to buy and own non-DRM books.
You can use Calibre to convert your ebooks to MOBI/AZW3, which Kindle accepts, and if you put your Kindle in airplane mode (so it stops getting OTA updates) and wait log enough it'll probably get a jailbreak at some point. At which point you can install KOReader for superior PDF/DjVu reading experience. Last jailbreak covers Kindle software <= 5.14.2; so Kindle Voyage and earlier all should be supported. (See https://www.mobileread.com/forums/showthread.php?t=346037 HN discussion: https://news.ycombinator.com/item?id=31220553)
This looks very promising. In addition to using KOReader I will be able to customize the lock screen and remove Amazon's upsells. I guess the only downside is that I won't be able to use WiFi or buy e-books from Amazon.
Also, Koreader runs on many brands of ereaders, so it may be worth exploring if you're interested. Kobo readers can read non-DRM epubs out of the box and can also run Koreader. Check out the MobileRead forums.
Here's the one for Kindles:
https://www.mobileread.com/forums/forumdisplay.php?f=140
Likebook mars, I got it in the 2018 for about 200$ and still using it today, is basically android with an e-ink display, so you can pretty much do anything with epub and pdf.
I don't buy drm crap, genesis all the way, I don't give a fuck, someone needs to come up with a better business model.
I got a Kobo and it does bookmarks, text selection and dictionary search fine. I shop from a variety of places, but only buy DRM-free EPUB books (https://www.ebooks.com/en-us/drm-free/ for example)
I use Calibre to organise the books (and convert formats if necessary) and push them to the device.
I backup the entire collection using a USB backup drive irregularly (once a month or so). I'm experimenting with Syncthing to backup to a rented baremetal server. So far so good.
The devices themselves are Android tablets, with an e-ink display. You can install and use any other Android ebook software, including among those, Koboreader, PocketBook, and FBReader.
My preference among those is actually Onyx's reader, at least on their own devices.