The wiki says:
Before centos-userland-release-7-5.1804, in order to activate the new kernel and edit /boot/extlinux/extlinux.conf, you had to run /usr/bin/update-boot. This is no longer valid and it is done automatically by grubby.
But I just happened to look at /boot/grub/grub.conf
default=0 timeout=5 splashimage=(hd0,1)/grub/splash.xpm.gz hiddenmenu title CentOS-Userland-7-armv7hl-generic-GNOME-1804 (4.14.28-201.el7.centos.armv7hl) root (hd0,1) kernel /vmlinuz-4.14.28-201.el7.centos.armv7hl ro root=UUID=be2c9311-e289-4cab-b878-89b522144d70 initrd /initramfs-4.14.28-201.el7.centos.armv7hl.img
And I did the yum update that installed the 4.14.52 kernel.
Should I run update-boot?
/boot/klist.txt has: 4.14.28-201.el7.centos.armv7hl 4.14.52-201.el7.armv7hl