In my Ubuntu 20.04 display settings on a Dell Latitude 7490 laptop, I can set my laptop monitor to 1920 x 1080 resolution at 60 Hz, but I cannot set my AOC CU32V3 32" 4k monitor to 60 Hz (see screenshots below), even though the monitor supports it. It feels laggy, so I'd really like to increase the refresh rate to 60 Hz. Any idea how I can do this?

Laptop monitor is 60Hz:

External monitor supports 4k (3840 x 2160 resolution) at 60Hz refresh rate, but I cannot set it to 60Hz:

Notice there's no 60Hz option:

Proof the manufacturer says it supports 60Hz at 4k:

https://us.aoc.com/en/monitors/cu32v3

Info on my laptop's graphics card (Intel HD Graphics 620):

I'm currently connected with a High Speed HDMI cable in HDMI 1.2 mode. Am I to understand that I must use a USB C to Display Port adapter and the Display Port to get 4k at 60Hz, perhaps, instead of HDMI?

Related:

1. https://www.dell.com/community/Latitude/How-to-have-Latitude-7490-to-use-4k-display-with-60Hz/td-p/6085124