I have Onyx Boox Page. It's pretty much the same size as your Sony, but it's sligthly wider because of the page turn buttons. It's also slightly thinner and the display is bigger due to smaller bezels. It has Android ~~12~~ 11 and Play Store so you can install any Android app you want.

Because it's not a dedicated reader device, but an Android device with an e-ink display, it's a bit more difficult to use than a typical e-ink reader. E-ink displays are slow to refresh and to overcome some of the problems caused by that, they have different refresh modes. Your typical e-ink reader chooses the best refresh mode for different use cases (reading, browsing the menus, etc.). Because the Page is an all-purpose Android device, the operating system cannot know which refresh mode is best for each app. That means that it's the user who has to decide which refresh mode to use with each app.

The Page has a quick access menu to change the refresh mode and other settings. These choices are remembered per app. You'll have to experiment with them to figure out the best (or good enough) settings for each app. The choices are basically between refresh speed and amount of ghosting: Faster means more ghosting. The Page has a feature that let's you bind long press functions to the page turn buttons. I highly recommend setting one of the buttons as "full refresh", so you can use speedier refresh modes and then just hold the button for 0.5 seconds (duration can be changed) to refresh the screen when needed.

Some Android apps are more e-ink friendly than others. You'll want to disable most animations and use paginated views instead of scrolling wherever possible. Unfortunately, most apps aren't optimized for e-inks, and while some of them have settings that makes them more convenient to use with e-ink screens, you pretty much always need to fiddle with settings and figure things out. As an example the Kindle app: If you swipe to turn page, there will be a page turn animation. If you look through the settings of the app, you'll find a setting called "Page Turn Animations". Regardless of if you enable or disable this setting, there will be a page turn animation. That setting just changes it to a different kind. But, if you use the Page's page turn buttons to turn the pages (instead of swiping) there won't be page turn animations regardless of that setting. Is any of that somehow obvious? Nope, but at least the app is usable, if your device has those page turn buttons. Without page turn buttons, those animations ruin your reading experience and you'll want to use another reader app instead.

Overall I really like the Page. It has it's quirks and you'll need to fiddle with settings, but Play Store with all of its apps outweighs the problems.

EDIT: Corrected the Android version.