Is it possible to obtain a VCP-DCV 2023 certification by passing the Professional VMware vSphere 7.x (2V0-21.20) exam and taking a V8 authorized training course?
Short answer: Yes.
Longer answer: If you go to the VMware Certification site ( https://www.vmware.com/content/vmware/vmware-published-sites/us/learning/certification/vcp-dcv.html.... ) and select VCP-DCV, then chose 'No VCP Certifications' on the left you will see the steps required.
Step 1: Gain Experience with vSphere
Step 2: Attend one of the required training courses (both v7 and v8 courses are listed.)
Step 3: Pass one of the exams (both v7 and v8 exams are listed).
So yes, you could take a v8 course and a v7 exam and you would gain the VCP-DCV 2023 cert.