Is there a way to codesign an Android Studio APK WITHOUT using Gradle?

Android Studio seems to reject Gradle 3.3 now, even when using the old versions and settings I managed to get to work a few months ago.

It can still be used to BUILD APKs, but code-signing them gets rejected with “The project is using an unsupported version of Gradle” now even using the setup that used to work.

Is there a way to codesign without using Gradle?

I may be missing something, and I hope I am and someone will let me know, but it seems like OF will be unable to post anything to the Google Play Store until/unless there’s a way past this.