All the line code available suggests you control this with the versioning i.e. e.g. 7.17 would be CPU and 7.18 would be GPU.

<app_config>
   [<app>
      <name>Application_Name</name>
      <max_concurrent>1</max_concurrent>
      [<report_results_immediately/>]
      [<fraction_done_exact/>]
      <gpu_versions>
          <gpu_usage>.5</gpu_usage>
          <cpu_usage>.4</cpu_usage>
      </gpu_versions>
    </app>]
   ...
   [<app_version>
       <app_name>Application_Name</app_name>
       [<plan_class>mt</plan_class>]
       [<avg_ncpus>x</avg_ncpus>]
       [<ngpus>x</ngpus>]
       [<cmdline>--nthreads 7</cmdline>]
   </app_version>]
   ...
   [<project_max_concurrent>N</project_max_concurrent>]
   [<report_results_immediately/>]
</app_config>

In Device manager you can set a device profile (school, work...) to use only GPU tasks and set this profile for a Device to use GPU only.

The code written by the researchers team has already been handed over to the WCG programmers for alpha testing, at least that is what the OP says of this thread ;o)

(WCG does not share source code BTW, but Scripps' AutoDock itself is open source)

Why posit it if you know the answer... would you tell "go take a hike" you Android / Linux Arm crunchers :?

It's a shame openPandemics isn't open source. If it was, it would support GPU by now.

I'm a little biased though. I built Quarantine@Home back in late Feb / early March. We started with the Linux GPU client (although never got around to supporting GPU in windows or osx. We're opensource though, and happy to take pull requests. All we really need is help compiling the GPU version in those other platforms : https://github.com/cjmielke/quarantineAtHome

If you are itching to put your GPU to use, and have linux, feel free to poke me if you want help. Our linux client is dependent on docker. Kinda wonky compared to the BOINC experience, but works, and we've got about 1 million docked poses now : https://quarantine.infino.me/job/861469/

Alternatively, install Folding@Home. They are actually taking all of the docked poses Quarantine@Home has found and performing much more rigorous free energy perturbation calculations to validate the possible hits.