Best way to deploy to mobile for testing?

I have created a few internal use only mobile apps. I would like to deploy these devices over our network. Because they are sensitive I don’t want them on any App store.

I certainly don’t want to connect all of our devices up over USB.

Any suggestions?

Can’t speak to iOS, but building and signing the .apk file and uploading it to a sharable google drive folder has worked for me in Android.