Hello @Yohan ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand that you would like to select the preview environment of Azure Static Webapp in your Azure Front Door Standard's origin, but it is not available. The Front Door's origin only lists the main/production environment.
Currently, this is a design limitation.
When selecting static webapp as the origin type in the Front Door's origin, it will only list the production environment.
It has been requested by other customers and the feedback is already under review by the Microsoft engineering teams responsible for building Azure. You can upvote for this feature in the below feedback forum or create a new feedback item requesting this feature:
https://feedback.azure.com/d365community/idea/f6437651-8a26-ec11-b6e6-000d3a4f0789
Workaround:
If you would like to add the preview environment, then you can configure an origin with custom origin type and add its URL as the hostname/host header.
Refer: https://learn.microsoft.com/en-us/azure/frontdoor/origin?pivots=front-door-standard-premium#origin
https://learn.microsoft.com/en-us/azure/frontdoor/how-to-configure-origin#add-an-origin
Kindly let us know if the above helps or you need further assistance on this issue.
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