> I can’t buy a cheap Linux tablet

much better, you can make one yourself! and considering touch displays out there (Waveshare have nice ones) already have supports to hook up your pi without much CAD tinkering, it's all about making a case and developing your system for a battery (which also are quite popular and have already made solutions). if we stop being prudes all we get is Jeff and Jobs locked devices! take a look at the cyber-deck scene on Reddit