"DP 1.4"
Here is your answer!.
DisplayPort 1.4a supports only up to 4k 120Hz refresh rate.
To use 4k 240Hz you need either DP 2.0+ with UHBR 20 transfer mode (77.37 Gbit/s), which is not supported by either your monitor, GPU's of RX 6000 series or RTX 3000 series as well iirc, because it is recent standart (and i am impressed by it's speed comparatively)
OR!, You can use HDMI 2.1 with DSC (display stream compression)
Those adopter issues... What even you will be able to play at 4k 240 fps?