Proxmox VE 8 to 9 in-place update but kernel still on 6.8

Success! These are the steps:

Bash:
umount /boot/efi
proxmox-boot-tool init /dev/disk/by-uuid/AED9-4562 grub
proxmox-boot-tool refresh
mount -a
reboot

After that the system rebooted with the updates showing kernel: Linux 6.17.4-2-pve .

Thanks for your help @Gilou, much appreciated :)