Is there a way to disable the prompt for Substitute Best Matching Printer Font?
Yes. If you are using a Seagull Driver, head over to File -> Print -> Performance Tab
Under Print-Time Error Handling, uncheck the option for Warn When Using TrueType Fonts
Disabling Font Substitution
If you need to disable font substitution altogether, you can do so by following the article here: Printed fonts differ from the label or document design