1. Download the fonts you want, so in my instance I downloaded:
ProductSans-Black.ttf
ProductSans-Bold.tff
ProductSans-Regular.ttf
2. Then drop then into this location:
/Users/NAME/Library/Application Support/Sports Interactive/Football Manager 2023/skins/fm23BaseTrans/fonts
3. Then open every file in the fonts folder above and replace the font name entry below with the fonts you've downloaded:
GT-America-Standard-Black
GT-America-Standard-Bold
GT-America-Standard-Regular.ttf
Obviously ignore any European Competition files if you want to retain the branding.
So for example in the actions_disabled.fontxml file;
Original:
New:
4. Once all done, load up FM23, clear cache, reload skin and enjoy...