OK, when I added that kernel option to my GRUB config, I then rebuilt my grub config: grub2-mkconfig -o /boot/grub2/grub.cfg. Finally, I ran sudo dracut -f to rebuild the initrd, as per that post. It threw me a suspicious error:
cat: /sys/power/resume: No such file or directory
Now, this sounds like it would make an issue resuming form suspend (which it the big issue I have), but oddly this Qubes forum post contains a reply from Qubes Team member @fepitre who suggests that the error may not be meaningful?
Regardless, I rebooted the system to try the new kernel options, and then suspended. The system did seem to go into suspend (perhaps a little deeper?) but I still cannot wake it up. I would love someone to weigh in who might understand what that dracut error means. In my digging for ideas, I did run into a github thread that sounds very relevant, but I am not quite yet savvy enough to fully understand where it leads.
I am working on it, and I like to solve it once and for all. Any help would be greatly appreciated by me, and also probably I imagine by a lot of Qubes users with suspend issues. It seems to be common on newer Intel hardware at least.