If you have ebooks in a number of different ecosystems, perhaps kobo, comixology, kindle, adobe digital editions, pdf, actual epubs, microsoft word documents, then it's amazing having access to the official apps to read those file formats and connect to the online services.
In the event you're not a fan of prorprietary Android apps, the BOOX also does F-Droid quite well.
(I use a mix of F-Droid and APK-Mirror sources.)
There seem to be a good set of mostly-works-on-eink apps on Android. Onyx's bookreader and note-taking apps (native and with better e-ink support) are also quite good. I've been disappointed by Linux e-book support on desktop, and the even smaller tablet space is quite probably worse.
Another available tool is Termux, and while no Linux replacement, it vastly increases the usefulness of Android devices.
I just ordered a boox max lumi, I noticed that there’s an option to install play services.
I am hesitant to do it, except for the security fixes Google apparently brings to Android via these updates. Boox might not update the device in the future which is my main worry.
The Max Lumi is what I picked up this past March. It's big, but an excellent choice for scientific articles, note-taking (a surprise --- not my intended use but one I'm finding I do make use of extensively), or reading comics at full-size.
Onyx updated the device once shortly after it arrived, but not since.
I've not been able to activate the Google Play Store ... I think because of Google's "you must register an account" bullshit, so I've just stuck with F-Droid and APK-Mirror for a couple of apps (mostly Pocket, as the F-Droid version is badly out of date).
Since I install few apps regardless, this is not much of a handicap, and I consider it a benefit.
There's no vanilla linux version of Libby, Kindle app, Kobo, Marvel Unlimited, Pressreader etc. At best you can maybe use a web browser for those which is a sub-par experience. For reading content Android is IMO better because there is general an app for DRM'd content. Linux doesn't have that and not all content can be made DRM free.
Have you used Linux on a mobile device? It is getting better, but it is not an enviable experience yet for your average user.
Take something like Spotify, for example. There is a desktop Linux client and an Android app. Guess which one works better on a small touch screen with only a bit of power?
Koreader has a lot of options but IMO the UI is perhaps the worst I've ever used. Also has giant use case gaps that will never be fixed like the fact it can't handle vertical Japanese writing.
(please correct me if there were more recent developments)