DP v1.4 does support 240Hz but at lower Resolutions.
Found this Cabe Tech article explaining about DP 1.4 and 240Hz Resolutions: https://www.cablematters.com/Blog/DisplayPort/does-displayport-1-4-support-240hz
![Screenshot 2024-08-02 122432.png Screenshot 2024-08-02 122432.png](/t5/image/serverpage/image-id/116234i601E98FE122D7F50/image-size/large?v=v2&px=999)
Note: the above chart shows why when you have your Monitor set for 2560x1440 Resolution, it supports 240Hz.
From Wikipedia showing the maximum Resolutions for 5K DP versions:
![Screenshot 2024-08-02 123351.png Screenshot 2024-08-02 123351.png](/t5/image/serverpage/image-id/116238i7DE6137DF9466BAD/image-size/large?v=v2&px=999)
EDIT: You will need a DP version 2.0 or above to get 5k with 1440 hz Resolution. DP 1.4 Bandwidth does not support 5k at 1440hz bandwidth.