This string refers to a specific for iOS, likely distributed as an IPA file for sideloading. Each segment of the filename represents a specific component, plugin, or version integrated into the build. Breakdown of the File Signature
Allows the app to continue playing audio after the screen is locked or while using other apps. 2.2.3_YTK _DEMC_AB_iSB_RYD_YouMute_YTUHD_18.09....
If you see a "Something went wrong" error on version 18.09, you may need to go into Settings > YTUHD and enable "Fix playback issues" . This string refers to a specific for iOS,