Hello Remy Raheste,
We have checked with the Engineering team that the feature is now registered for your subscription.
Please run the following command below :
az provider register -n Microsoft.Compute
After that, try re-run this command:
az feature show --namespace Microsoft.Compute --name SIGSharing --query "properties.state"
Please share your output. once you’ve completed these steps.
Please let me know if you have any queries.