I spent months trying to figure this out and using different libs and files. But dont need to do that even on Apple Silicon I was able to get it working on a M1 mac.
1. Connect both left and right controllers in bluetooth menu
2. Hold Capture and Home buttons on controllers for 5 seconds (this joins the controllers together in bluetooth mode) ~ This is the most important part
3. Open Steam and disable steam input on Stardew Valley
4. Start Stardew
5. Enjoy!~