I have tried to uncomment only those two lines:
# hdmi_group=1
# hdmi-mode=4
on an default EndeavourOS config.txt, no success. Then after that I have tried all kinds of combinations among other:
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=82
and
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=400000000
Those last two work on raspberry pi os but not on EndeavourOS unfortunately. At least not for me.