Welcome to the community.
For ELRS you also need RC_OPTIONS bit 13 (value 8192, “Use 420kbaud for ELRS protocol”) for the right baud rate and I would recommend bit 5 (value 32, “Arming check throttle for 0 input”), resulting in RC_OPTIONS = 8736
It’s in the wiki: Crossfire and ELRS RC Systems
And in the forum: Pixhawk 6c with Elrs - #2 by Janno