@NortonAntivirus I highly doubt that the SKR v1.4 is able to read two encoder signals reliably. It takes a certain "hardware encoder" MCU (eg. STM32 gen4) to do it smoothly without interrupt-flooding the FW-main loop.
OTOH, IF a second linear encoder works on a CoreXY, I don't see a reason why it shouldn't work on a SCARA: the relation between motor steps and gearbox output IS linear. (but they are angles...)
You mentioned in the other thread, only one gearbox has such high backlash. For me it sounds like a warranty case?
I'd rather look for a replacement than going the wacky backlash compensation route.