In case anyone wants to play: a 16-bit sRGB file, with the max Y level that avoids clipping the blue component (the darkest primary).
Now, when raised by 4 EV and tone-mapped:
Darktable’s filmic v7, defaults (only auto-picked white and black relative exposure):
highlights saturation mix: -50%
highlights saturation mix: +50%
v5, no preservation:
sigmoid, defaults (per-channel, preserve hue: 100%):
per-channel, preserve hue: 0%
rgb-ratio:
smooth preset (some attenuation, some rotation of primaries, plus a bit of skew to preserve highlights):
