A friend let me know about an alternative to the ST series - an ARM Cortex M33 system by Renesas

It looks ideal going by the specs (and that is one sweet eval board), so I'm going to work on getting their dev environment set up and my current code working on it.  A lot will depend on BOM impact - this is actually supposed to be cheaper - so if it proves as workable as I hope, this could reduce the expected cost while giving better performance and better power savings.

The ESP32 I initially planned to use simply wasn't able to drive the LCD fast enough.  The SPI speeds are compatible, but blitting a 400x240 buffer at anything more than 8-10FPS resulted in a ton of glitches and artifacts.  On top of that, the amount of I/O to deal with (I was originally including two separate GPIO expanders / key matrix controller chips just to handle it all) was just not ideal.  Switching to an ST or Renesas option gives me the option of 100 or 144-pin TQFP packaging with enough GPIO to handle everything and then some.  As a bonus, comms becomes separate from the core processor which can only aid security.