GrapheneOS is stock Android without any tablet mods. As its such a nieche, AOSP sucks extremely on Tablets. If you want to try how it sucks, run Waydroid on your Linux machine.

Many apps dont display well like they whould. Firefox for example has no adaptive Tablet UI, so Chromium / Cromite / Brave are the only good options.

Pixel Tablets are awesome though, as they are secure and well documented. Could be great ARM linux tablets, for some modern system like Fedora Silverblue. On Tablets I would say GNOME is superior, both are not really ready yet. KDE Plasma mobile looks great too though