The EDID in your logs from Dell U2718Q monitor decodes to reveal this modeline:
Detailed mode: Clock 533.250 MHz, 609 mm x 349 mm
3840 3888 3920 4000 hborder 0
2160 2163 2168 2222 vborder 0
+hsync -vsync
That video mode is correct for reduced vertical blank 3840x2160 @ 60Hz (FOSS modeline calculators are not completely trustworthy or up-to-date).
And it is the mode you require…
But for some reason the Nvidia driver does not list this modeline at all…
Bit sad when even the most basic function (EDID) does not work properly.