It seems to be missing (according the manual which does not mention it) an SD card tray for microSD's to extend the internal 250GB storage, which is certainly a disappointment for me.
However the manual does specify lower specs than are presented on the website of TCL itself (such as Android 13 compared to Android 15). The manual might not be up-to-date. And it might be located on the underside of which no pictures can be found however
UPDATE: The Nxtpaper 12 Plus and 14 do not seem to have memory extension possibilities either and limited to 250GB. Can you confirm that @Quoth?