Unable to delete Automation Workspaces or DevOps organisation when trying to close tenant

Question

We have merged companies and no longer have need of our Azure resources or Azure DevOps organisation.

In shutting down the tenant, we've removed all resources, with a few exceptions, for which we need support:

1. A Recovery Services Vault (which continues to retain soft deletes, despite that option being off on the RSV) configuration.
2. A Front Door and CDN profile, and Endpoint: These are linked to a DNS service which we no longer have access to. Stack Overflow suggests:
   az feature register --namespace Microsoft.Network --name BypassCnameCheckForCustomDomainDeletion
az provider register -n Microsoft.Network
   And removing via the CLI. This produces the same error - so we cannot remove the resources forcibly - due to configuration that exists outside the Azure plane: ergo - incurring costs for something that is out of our domain of control.
3. Two Automation Accounts - which are not able to be deleted because of existing links to a log analytics workspace that no longer exists. The documentation suggests that unlinking the account should work seamlessly, given the LA workspace no longer exists. It produces an error when trying to unlink via Automation Account > Related Resources > Linked Workspace. Please provide support.
4. An Azure DevOps organisation (as an Azure resource), that is unable to be deleted because it is associated with a billing profile. The documentation suggests a role needs to be applied: Project Collection Administrators. This is an Azure DevOps specific role - so it doesn't seem possible to assign this role from outside the organisation - which even as an Entra ID global admin, we can't seem to do. We have already removed all user accounts in preparation for closure of the tenant.

The above 4 issues are preventing full closure of the tenant. I am unable to delete or remove the associated subscriptions until these resources are fully removed. If a support engineer is able to force closure of the tenant and billing account - or provide guidance on how to do so assuming ALL necessary Entra ID permissions are available (not Azure DevOps specific permissions, which we can't access via https://aex.dev.azure.com/ as it doesn't seem to exist), that'd be much appreciated.