I have the same problem as LeeG. The flow takes 5-10 minutes to complete but the flow ends with the error "The group alias already exists. Please choose another one".
I tried multiple times with new group aliases but always the same error.
Creating a site without a group has always worked for me.
@Evgeniy unfortunately this has taken too long for my company to wait for, I have had to move on to using a Graph API solution instead. The support response time was too lengthy for a company of our size to rely on this for business critical work.