What is the output of "grub2-editenv list"?
As mentioned:
# grub2-editenv list
saved_entry=2dc3a3c6f8494c8fb93c27f99dc3a246-5.3.8-300.fc31.x86_64
boot_success=1
boot_indeterminate=0
kernelopts=root=UUID=ac6336b1-7fd2-43d7-af44-51b592f3ab8f ro rhgb quiet
The saved_entry field matches what grubby shows - From everything I can see it appears
correctly configured. As I mentioned in my original post I've even moved all the
config files aside and reinstalled grub so that it would return to defaults.
I've now been reading
https://systemd.io/BOOT_LOADER_SPECIFICATION but cannot find
anything related to this problem. Everything looks OK.