QMP takes a single client and the web UI holds it for its whole lifetime, so this is the normal outcome while the page is open rather than a broken emulator. Verified against a private instance: 128x64, 1819 pixels lit, 64 rows of ASCII.
tools/panel_dump.py prints the display controller's own memory as ASCII or PNG for any firmware, with the four mappings, so two builds can be compared instead of glanced at. The panel model gained a bounded UVK5_PANEL_PROBE diagnostic along the way.
Measured: the 5.9.0.CN panel agrees with its own framebuffer 8188 of 8192 pixels with the data untouched, and the fetched 6.0.0 build renders identically. Both program the same geometry registers, which is why the mapping is a driver convention and cannot be derived from the controller: it has to be measured.
Noted, not yet fixed: the display start line (0x40|n) is ignored, and the model stores pixels at col-4 with the column counter wrapping at 128 instead of the controller's 132 columns.
mckero