Thank you for reaching out about increasing the number of free-tier Static Web Apps per subscription.
Azure limits each subscription to 10 Static Web Apps on the Free tier, and this limit cannot be raised, even with a Developer Support Plan.
To use more Free-tier apps, you will need to create additional subscriptions, as each one allows up to 10 Static Web Apps.
Alternatively, upgrading to the Standard SKU gives you the ability to manage more apps within a single subscription, along with higher quotas and production-level SLAs.
Reference:
https://free.blessedness.top/en-us/azure/static-web-apps/quotas
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