Forza 5 during start checkout returns error FH301 - the video driver needs to be updated. Discovered 20.45.40 required 21.10.1
Error 173 – No AMD Graphics Hardware Has Been Detected in Your System Configuration. What else could help?
you can try this UNOFFICIAL Windows Bootcamp driver where the Author modifies the latest AMD Driver to work in MAC Computers: https://www.bootcampdrivers.com/
If that doesn't work then you will need to open a Apple Support Ticket and see if they have a newer version.