Debian 12 stuck on GRUB after upgrade from Debian 11

Hi there!

I upgraded my Debian 10 install to Debian 12 this weekend, it rebooted successfully into Debian 11 after the first upgrade install, however after the second install the GRUB boot loader just sits frozen at; **Welcome to GRUB!**

The OS is running on a OVH 2018 VPS SSD 3 instance. I have tried booting into rescue mode and follow the steps to "fix" as described below, however to no avail.

https://help.ovhcloud.com/csm/en-public-cloud-compute-repairing-grub-bootloader?id=kb_article_view&sysparm_article=KB0051061the bootloader, however to no avail.

I have had this issue in the past going from Debian 8 to 9 and OVH support were kind enough to get GRUB loading again, however I am being told today that OVH does not do any OS support whatsoever -- contrary to their own support pages;

_If the KVM shows that the VPS is stuck in boot or unable to find the disk, ensure you have boot logs enabled. Relay the pertinent logs to our support teams for further investigations by creating a support request._

https://help.ovhcloud.com/csm/en-vps-check-file-system?id=kb_article_view&sysparm_article=KB0047545

Anyway, I just want to sort the issue. Anyone pointing me in the right direction would be greatly appreciated!

Thanks,
M