Quest for a new EasyFire flame detector sensor and overriding the broken photo sensor

tl;dr: Siemens photo resistive flame detector QRB1B-A070B70A is a suitable replacement for the Danfoss 057H7101 LDS sensor, that is so end of life, that I couldn’t even find it’s datasheet anywhere on the net. It did cost me 35 EUR. Every time the central heater breaks down it’s in the wintertime and on a holiday or vacation. It’s probably some sort of law. So I was not amused then the heater started throwing up showing error messages of the sort “No flame detected”. This sometimes happens and it’s usually enough to simply reset the system to start another burn. It’s an older pellet system by KWB called EasyFire. I’d not go for such a system again but back when this was hot (haha, sorry) people were trying to sell me gas or oil instead and look where that went 😛 Anyway, I knew something was up when the errors started to pile up. Every time I checked the firebox I found no unburned pellets and only ashes so starting the fire was not the problem (this time) so I checked the flame…