Note that ELRS (or is it CRSF? Dunno) restricts channel 5 to a boolean high/low PWM output. You cannot use this channel for anything else. Your TX handset controller will show the PWM output you expect, but on the receiving end, you’ll only get low or high.
This is because ELRS, with the God-given right to decide what everyone does with their radios, determined channel 5 would only be for arming.
Version-dependent
I’m told this changed in ELRS v4.0 and is no longer the case, but haven’t been able to verify that myself.