'According to
https://onyxboox.com/ they use DC lighting with "flicker free" technology. Could it be something else?'
Interesting. I'd assumed PWM as I've seen a few ereaders that say they have non-dc-dimming PWM lighting (e.g. Bigme). I did find the Palma lighting too bright on its lowest setting and too cold. Also, there's still often PWM between the steps of DC-dimming lighting but I think that's generally thought to be a non-issue. Maybe BSR plus the lighting was an issue for me.