This gives me a QHD display on my RPi 4, this is the whole config.txt

[pi4]
kernel=9pi4
arm_64bit=1
[pi3]
kernel=9pi3
arm_64bit=1
[all]
gpu_mem=16
core_freq=250
enable_uart=1
boot_delay=1


hdmi_group=2
hdmi_mode=87
hdmi_cvt=2560 1440 60 3 0 0 1
max_framebuffer_width=2560
max_framebuffer_height=1440
hdmi_pixel_freq_limit=250000000

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