Most answers assume users to have Android Studio, which I do not have and do not want. Any way to fix this without?

Yes, you don't have to install Android Studio.

For your existing Android project, I expect that you already have local.properties under your root dir of your project. Open and modify there to set your NDK dir. E.g.

ndk.dir=<< your-path >>/Android/android-ndk-r16b

sdk.dir=<< your-path >>/Android/sdk

Most answers assume users to have Android Studio, which I do not have and do not want. Any way to fix this without?

Yes, you don't have to install Android Studio.

For your existing Android project, I expect that you already have local.properties under your root dir of your project. Open and modify there to set your NDK dir. For example, your NDK version is android-ndk-r17b (https://developer.android.com/ndk/downloads/), and you have installed (or unzipped) it in directory /Users/myname/foo/xxx/Android/android-ndk-r17b, then modify this file as below:

ndk.dir=/Users/myname/foo/xxx/Android/android-ndk-r17b 
sdk.dir=/Users/myname/foo/xxx/Android/sdk