[iMore Question]

I have read what is available on the topic and looked at the various screens but I seem to be missing something

[Just_Me_D]

If you're asking whether or not you can back up your iTunes library to your iCloud Photo Library then the answer is no. If you're asking whether or not you can backup your iTunes library to your iCloud Drive then the answer is yes or at least you should be able to. Having said that, my interpretation of "iTunes Library" is the same as that found via the following link.

https://support.apple.com/en-us/HT201610