grub-efi-amd64-signed package post-installation script subprocess returned error exit

[stevef]

So does that mean that any future package update I should worry about, because the system will install them anyway?

For this message only - retry the update/upgrade process and post back in your original thread.

Updating and upgrading is a complex business and works remarkably well most of the time.
However all error messages should be treated individually.

The message you have reported your original thread was previously reported by users doing their first upgrade of a new 7.4 installation.  After some investigation the cause appears to be one of the commands being run by the update/upgrade sequence unexpectedly requesting user intervention.  Behind the scenes, in this case, it appears that the update/upgrade completes despite the message.

Coming from Windows, I'm not familiar, and do not understand the GRUB/bootloader and where it is situated/installed.

Any questions please ask.