Hello Laurent van Mastrigt,
Thanks for your question.
This is usually caused when the resource SKU you've selected, such as VM size, isn't available for a location or zone.
If a SKU isn't available for your subscription in a location or zone that meets your business needs, submit a SKU request to Azure Support.
This is gotten from here: https://learn.microsoft.com/en-us/azure/azure-resource-manager/troubleshooting/error-sku-not-available?tabs=azure-cli#solution
Regards,
Abiola.
You can mark it 'Accept Answer' if this helped.