On 12/6/19 2:06 AM, Anthony F McInerney wrote:


On Thu, 5 Dec 2019 at 19:04, Samuel Sieb <samuel@sieb.net> wrote:
On 12/5/19 8:02 AM, Robert McBroom via users wrote:
> Updated from Fedora 29 to 31 on a legacy system.  Kernel updates no
> longer update grub.cfg to the new kernel.  Ran grub2-mkconfig -o
> /boot/grub2/grub.cfg which finds Windows and Centos 6 but none of the
> Fedora kernels.  /boot is in its own partition and the Centos kernels
> are in the Centos partition on a second drive. A backup of windows 7 on
> a usb drive is even found by os-prober. Everything these days seems to
> point to uefi systems.

grub has been switched to use BLS.  Check if you have files in
/boot/loader/entries/.

That's interesting. First i've heard of BLS. 
It would seem that runs into a known issue
https://bugzilla.redhat.com/show_bug.cgi?id=1652806
And the way tl;dr is "on BIOS systems you have to run 'grub2-install /dev/sdX'
Not installing grub, getting grub to recognize system entries.