I don't know if that changed recently. I gave up on it a year ago. I went through all this (though with Ubuntu not Fedora), switched modes, disabled secure boot, read every web page I could find. Nothing worked. I'm kinda tempted to see if I can get it working now, but honestly, also kinda traumatised by the whole experience and never want to touch it again.

I'm not familiar enough with Ubuntu's installer capabilities, but Fedora's has made huge advances in the past 5 years. I went in to the setup fearing the worst (that is, the struggle that was doing a secure boot, UEFI Windows 8 + Fedora 20 setup in 2014), but was shocked at how good Fedora 31's install routine was.

I shrank the 1TB SSD partition in Windows, disabled the proprietary fake-RAID, then booted Fedora's XFCE spin from a USB key. The installer handled everything else--no having to manually tinker with the UEFI partition. Post-install, the XPS's UEFI correctly booted to GRUB, which had successfully detected the Windows bootloader (again, no tinkering like with FC20) and can boot either OS.

Disabling hibernate in Windows and figuring out how to mount the encrypted Windows partition in Fedora was all that remained.

The Linux Kernel 5.5 has a bunch of improvements for the i7-9750H (and other Coffee Lake processors), which is another reason to consider giving Fedora 31 a spin. :)

I had this pleasant experience the same time I was trying to figure out how to dual-boot FC31 on a touch bar MacBook Pro. The short answer is: 80% of the MBP's hardware doesn't work in Linux. Broadcom won't release drivers that are compatible with Linux and blame FCC rules for their reason. Insane. https://github.com/Dunedan/mbp-2016-linux

dammit, now I'm tempted to try again. Thanks, I think ;)