This is one of the very few surviving open-source players still optimized to support Android 4.0 and higher. You can securely find and download it on the SkyTube Legacy F-Droid Page .
YouTube for Android 41.2 — Uptodown Update youtube for android 41 2 uptodown upd
If the official app remains unusable, these alternatives are popular in the r/androidafterlife community: Older versions of YouTube (Android) | Uptodown This is one of the very few surviving