If the app is relatively simple (like a tool or a game), consider rebuilding it as a Progressive Web App (PWA) . PWAs run in a browser but feel like a native app. They work on both Android and iOS without needing separate APK or IPA files.
Are you a looking to port your own app, or are you trying to run a specific app on your iPhone? How To Convert APK To IPA File - Step By Step convert apk to ipa