What's the best way to include a build number for Native App Google Analytics tracking?

I understand how to send the App Version number, but not being able to filter on the App Build number is becoming increasingly difficult. Is there a best practice on where to include the Build Number?

Would it be to append it in parentheis in the 'App Version' variable or as a custom metric? Not sure what would be best.

I'm doing this for both an Android and iOS implementation.

Thanks in advance!

Can Google Analytics track data from mobile apps?

To get the latest mobile app report features in Google Analytics, use Firebase in your Android and iOS apps. Once enabled in your app, Google Analytics will automatically collect and report on built-in events and user properties. You can also log custom events and set custom user properties.

Where should the Analytics tracking code be placed in the HTML of a webpage to collect data?

Answer: Just before the closing </body> tag of your website.