Hello, @Dominik Mańkowski !
How to check in which zones in a region VM size is available?
Using the az command you listed is the correct approach for determining if a SKU is available in a region. The issue you are running into here is that the HBv4-series was just released in June of 2023 and when we check the Azure products by region page, we see that it is not yet available in West Europe:
https://azure.microsoft.com/en-us/explore/global-infrastructure/products-by-region/
You would need to deploy either in East US for the time being or use an HBv3-series VM in West Europe.
I hope this saves a bit of time in searching and thank you for your interest in the HBv4-series. Hopefully it will be available locally in the near future.
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