@RodrigoN, if your kernel version (which can be displayed in Terminal via uname -r command) is below 5.0.x, and your initial Ubuntu distro was 18.04 or 18.04.1, you don't have HWE installed. As stated here:
"The [HWE] stack consists of a newer Linux kernel [meaning, v5.0], X.org graphical server, and graphics drivers. These weren’t automatically installed ...
If you are still having a problem with display drivers you can try: sudo ubuntu-drivers autoinstall
Or if there are any other problems with drivers or packages during the boot run: sudo dpkg --configure -a
TLDR; Triple check that your cable supports 60Hz.
Having struggled with this issue for a while now, I would like to point out that it is not you, not the monitor, not Linux but very likely the cable. A few months ago, I have even brought a perfectly fine, brand new 4K monitor back to the store because I thought I could not use it (30Hz is just unacceptable ...
After several days of tinkering and trying several configurations, I would like to share the scripts (commands) that I've set in order to configure my desktops properly.
First of all, I have two screens:
- Laptop Screen 3840x2160 (4k)
- External Monitor through docking station 1920x1080
- Laptop panel will be "on the left" while the External monitor is on ...