Installing Ubuntu on a G5 5590

After using it with Windows for a couple years now, I recently upgraded my internal SSD from 512GB to 2TB, and I want to install the latest Ubuntu or Fedora my system, but I have several concerns:

1. It's been ages since I've done a dual-boot on a laptop, and the last time I did it, UEFI was not around. What I want to end up with is a laptop that can dual-boot both Windows 11 and Ubuntu or Fedora, but also preserves the recovery utilities should something blow up with Windows. Can I trust the install process to respect that, or do I have to point it to the Windows boot loader manually, and if so, how do I do that?

2. If I have to turn Secure Boot back on just to be able to boot into Windows, will I need to do something so that the Nvidia drivers are made Secure Boot-friendly? 

Although I do have a moderate degree of knowledge about installing Linux, I have in recent years refrained from doing it on modern hardware. I absolutely hate dealing with UEFI and Secure Boot, and after going through the nightmare of trying to install it on a desktop where Secure Boot is always on, I'm reluctant to try it here. AFAIK, I can still disable it if necessary, but I rarely find myself in UEFI to check. Any assistance would be greatly appreciated.