LL6.0 installs but after update get X.509 error @boot; LL6.6 install screws PC

[stevef]

Glad you got it sorted.

Looks like formatting the NTFS partition in LL is corrupting it and upsetting Grub/boot. Could the reformatting change/damage the GUID?

If the Windows doing the formatting has worked, then perhaps Windows is doing something different.
I've not had problems getting Linux to format NTFS drives in general, but it is sound thinking to get Windows to do the MS proprietary jobs when possible.

Out of interest, does the log still report these after good Linux boots
"Problem loading X.509 certificate -65"
"Error adding keys to platform keyring UEFI:db"