Hi Thomas,
this is a very grey zone. You could do so for customers if Azure Local and AVD are the technology running on your owned hardware and the customer accessing a "customer solution" on this.
HW and Subscription is owned by you as provider for the customer solution.
If it is rather a regular hosting than this is forbidden by product terms.
Your additional layer with each customers has its own tenant indicates a wish for classical hosting, doesn't it?
You might want to connect with the CISPE which has more insights on the "multi-tenancy" of Azure Local. There is a non-public agreement to which CISPE members have access, too.
I have been told by the general secretary of CISPE that members shall receive access to a kind of preview.
The other option is you are providing AVD on Azure Local on dedicated HW per each customer.
You manage (managed service) for customers under their subscription. This is valid and does not invoke the customer solution.