UPDATE! here’s how I got it to work:
I don’t know if this is documented anywhere but I couldn’t find it and would have appreciated knowing this 2 days ago.
1- Rather than the version of Android Studio recommend in the unreal documentation (3.5.3) I downloaded the latest version (4.1.2)
2 - the Oculus documentation (https://developer.oculus.com/documentation/native/android/mobile-application-signing/) just says “In Android Studio, go to Build > Generate Signed Bundle / APK.” This isn’t clear enough. I had to open Android studio and open>[Unreal Project]>Intermediate>arm64>gradle
3 - when open (mine wouldn’t open in ASv3.5.3), then Build > Generate Signed Bundle / APK
4 - the generated/signed apk was saved in gradle>app>app-release.apk
5 - When I only selected v2 signature Oculus didn’t accept the apk as signed, even though the above docs say selecting just v2 is fine. I had to select both v1 and v2 to get a build that the site accepted.
I hope that helps someone else save some time.