Source that YouTube makes a profit?
Someone who is in finance/accounting can probably read this better than me, but my rudimentary review indicates they make a profit here.
Alphabet Q3 earnings report (they also have them for the last few quarters and last year)
Revenues: Google Services $ 67,986
Operating income: Google Services $ 23,937
Google Services includes products and services such as ads, Android, Chrome, hardware, Google Maps,Google Play, Search, and YouTube. Google Services generates revenues primarily from advertising; sales of apps and in-app purchases, and hardware; and fees received for subscription-based products such asYouTube Premium and YouTube TV.
Google Cloud seems to be operating at a loss/barely profitable, with their 'Other Bets' making a loss too. 'Services' which includes YouTube, seems to be profitable. It isn't isolated in their own breakdown, but indicates profitability to me.