アイコン変更のソースはこれだから読んでね
https://github.com/ReVanced/revanced-patches/blob/main/src/main/kotlin/app/revanced/patches/youtube/layout/branding/CustomBrandingPatch.kt
https://github.com/inotia00/revanced-patches/blob/revanced-extended/src/main/kotlin/app/revanced/patches/youtube/layout/branding/icon/CustomBrandingIconPatch.kt