Android is a massive value add. I can’t tolerate it for my actual phone, but it’s just an absolutely huge step up from the other ereader OSes.

I’m using a Boox Leaf 2 myself, it’s basically just an android tablet with an eink screen. I can load pretty much any eBook format, and you can put regular android apps from play store (or any other app store) on it as well if you want. And they have a microSD card slot available from the outside to expand storage.

All the hacks and mods people do to their kobo are not needed, because it’s supported by default on my Leaf 2.

I’ve looked into those other brands but not recently enough to provide any meaningful comparison. (though I have this feeling that “remarkable is overpriced” is something I’ve heard a lot, but I could be wrong)

I’ve personally owned the Kobo Glo, Glo HD, and Libra 2.

For most of their devices (I can’t speak for current models one way or the other) you can swap out key bits of the software and enhance functionality via various hacks/mods. A lot of that is documented here: https://www.mobileread.com/forums/forumdisplay.php?f=223

You can also open them up and replace a standard SD card to boost storage capacity. (Again, I know this to be true at least through the Libra 2, I do not know about more recent models.)

The thing I got the most use from in the past was being able to swap out the sdcard on my Glo and Glo HD, but some folks really swear by the other various mods. I don’t have any complaint with the default reader software on the Kobo, so haven’t messed with swapping that out.

I have not messed with the SD card on the Libra 2 for two reasons - apparently doing so will mess up the waterproofing, and also because I’ve found 32GB to be sufficient for my purposes.

I went with a Boox device recently and like it. Since it is just android you can load up all sorts of apps. I use it for various things other than reading books, for example with the Paprika app in the kitchen as a recipe display.