The Pokémon Company has not released a mobile port. Any "APK" file is likely malware or a fake application designed to display ads.

I can, however, help with a safe, useful blog post on legal alternatives and related topics. Here are three options — pick one and I’ll write the full post:

Downloading the APK (Android Package File) allows you to install and play the game on your Android device without purchasing it from the Google Play Store. However, please note that downloading APKs can pose risks, such as malware and pirated content.

Pokkén Tournament DX : Official Availability and Playing on Mobile

If you want the closest experience to an APK on your phone, use :