Thank you for your reply.
I already stopped and started this VM multiple times, even tried to redeploy and reapply it to no avail. Even the Serial console is timing out. I cannot see starting logs or kernel panic. I just started this VM in Azure portal, it took more than 1 hour for the portal to show it as "started" with errors showing in notifications :
Failed to start virtual machine '<redacted>'. Error: ajaxExtended call failed
Still not possible to access serial console from the portal.
I had hopes 2 days ago as I tried to redeploy the VM and it failed with the following message :
"We're sorry, your virtual machine isn't available and it is being redeployed due to an unexpected failure on the host server. Azure has begun the auto-recovery process and is currently starting the virtual machine on a different host. No additional action is required from you at this time."
But 2 days later I am still in the same situation.
I just enabled "Guest Monitoring" diagnostics but the extension agent cannot be installed on the VM as the host OS is not running. I am at loss here because I am pretty sure the host is not starting at all but the portal is showing a "started" status despite the OS not even starting. Also opening a ticket to support is not possible as the portal checks for availability and returns only green checks.
I was able to open a support ticket today so I will continue this with Azure support.