Package github.com/AzureAD/microsoft-authentication-library-for-go in version v1.5.0 has issue about issuer validation of assertion id_token for Workload Identity in AKS run in Azure China Cloud. Bug is already fixed in version v1.6.0:

AzureAD/microsoft-authentication-library-for-go#589

This is possible regression of fluxcd version 2.7.2 and 2.7.3 where that package version is used.