It sounds like you got it figured out, but these are some related facts,
NEWDISPLAYTYPE in localize.env can be one of,
hdmi, dsi, st7789, ili9486, mhs35, ili9341
DSI screen MUST be 800x480, this assumption allows me to hard-code
gpu-efficient planes/scales
HDMI screen could/should be 720p, and will fall back to lower
resolutions if 720p isn't available
if it helps,
-craig
KM6LYW