Since the recent update to App Store Connect, I can't figure out at all as to how I submit a new TestFlight build for beta review.
Under 'iTunes Connect Users' it says 'Ready to Test', while under 'External Testers' it says 'Ready to Submit'.
Maybe I'm missing something obvious, but how do I submit for beta review? I already have multiple versions on TestFlight.
Discovered the answer, the key was to go on iTunes Connect > My Apps > TestFlight > Any Group > Builds, and then submitted it via adding a new build in there.