Well, the case here for paid support (prior of Qubes installation) is an interesting one where nothing is actually existing to cover such support need.
From a technical perspective, that would fall into the “hardware enablement” which is difficult to realise unless the “supporter” also has access to the hardware, or get a lot of logs from the user to be able to “guess” what is the cause of a problem and resolve the issue. Easier locally to document and test, and then create documentation to be replicated by remote user.
For other support use cases where Qubes in installed and working, a tool was developed under grant by Qubes and Whonix collaboration (and Insurgo for getting grant…), which permits remote control of dom0 over tor hidden onion service provided through whonix, if the user installs the server components under dom0, starts manually the service and shares with the trusted third party administrator an automatically generated secret through a preestablished trusted communication channel. You have to understand here that trust to the remote admin is implicit and delegated.
The documentation for the remote administratiom tool is under Whonix here: Remote Administration - Whonix
As you can understand here, liability, trust and responsibility issues are not resolved in the software itself, which is delegated to offline established trust. Let it be a friend, or an already trusted IT team member, to resolve on the spot issues, in the form of on demand and explicit support requests from users.
The creation of "trusted Qubes remote admins, as of today, doesn’t exist. There is no “suggested paid rate” nor “recommended paid support providers” either. But the tool exists, with associated risks. One of the goal was to be able to create such paid service.
Note that the tool is slow, because it is bound to VNC over a tor hidden onion service. It should be considered as a first step into scoping the remote admin needs, and is not necessarily optimized for the actual use case. It should be used carefully and improved through usage, by those who needs it.
Also this topic: https://forum.qubes-os.org/t/qubes-remote-support-new-features-and-support-for-whonix-16