Quick and dirty is this:
Running a new dual boot system. Windows boots fine and fast. Grub bootloader grinds and grunts to startup. Systemd checks point to Fedora waiting on the Win10 disk to boot (+45s!!!). Obviously, I don’t need that drive to run, but Fedora/Bootloader thinks it should.
Disconnected the Win10 drive, Fedora booted in 3.6s.
So… Windows bootloader knows to ignore the Fedora OS drive and launches fine. Fedora Bootloader insists it try everything to get that Win10 drive running to my own detriment.
Is there a way to just ignore the Win10 drive the way Win10 ignores Fedora?
Been scratching my head on this one for a bit to be honest.
EDIT: Seems the issue was caused by RAID incompatibility from my internal backups for Win10. The RAID drives wrongly pointed the finger at the boot disk because the only thing I could really make sense of in diagnostics was the Win10 boot stalling for 45+ seconds. Once I disconnected all the drives and incrementally reconnected them I quickly realised it was the backup drives and not a boot disk conflict as I wrongly assumed.
Nope!
Root, Boot, /EFI, /home
After writing this post I took the nuclear option and disconnected all drives in the PC save for the one hosting Fedora. Then I incrementally connected them all until failure.
It wasn’t the Win10 drive but the RAID pair I have as a system backup causing the problem. I guess Fedora was trying to mount those disks causing the hold up. Then that made it look like it was the Win10 disk causing the holdup because it was waiting to initialise.
With the RAID drives disconnected everyone is speaking the same language now.