Welcome to Microsoft Q&A Platform, thanks for posting your query here.
RHUI is a clone of Red Hat repository. So it is basically the same. However, RHUI is intended to be used for PAYG RHEL. So "everything" may not be the same as you are thinking because Microsoft PAYG RHEL is not covering all the Red Hat products.
Ref: https://learn.microsoft.com/en-us/azure/virtual-machines/workloads/redhat/redhat-rhui
Hope that helps.
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