Frsky passthrough doesn't work as described

Has anyone managed to run frsky passthrough on Cube Orange - using serial option 7 or 15 (invert TX/RX , half duplex etc.)
Today I’ve made an experiment to check this funcionality and nothing work as described on wiki .I’ve tried all the configurations,ne west firmwares etc. Works only with ttl<>RS232 converter.
Could someone share experience on this matter .

A simple 10k pull-down resistor will work. In fact almost any value from 2k to 10k.