Pine64 is considering a budget Linux smartphone running KDE Plasma.
Pine64 has already created a budget laptop called Pinebook. Creating a Linux-based tablet running on ARM-board should not be a difficult task for them. In fact, PineTab will be released before PinePhone.
The targets price should be in $100+ range for 2GB RAM and 16GB storage configuration. https://itsfoss.com/pinebook-kde-smartphone/