For users on iOS 12.5.6, your best bet is to find a clean version of YouTube++ or a plain, old YouTube IPA (versions 16.32.6 to 20.23.3).

Jailbreaking iOS 12.5.6 opens up permanent fixes. You won't have to re-sign apps every 7 days, and you can trick the official App Store version of YouTube into thinking it is running on a newer iOS firmware. Step 1: Jailbreak iOS 12.5.6

: Use AltStore or Sideloadly with uYou. This requires weekly refreshes but keeps your device stock.