Kind of: their edge-cache appliances run FreeBSD. IIRC they run Linux on their Amazon cloud for all their 'internal' stuff.
If you do some searches there's some good presentations on their work on getting encrypted streaming to go Very Fast:
* https://www.phoronix.com/scan.php?page=news_item&px=Netflix-...
* https://2019.eurobsdcon.org/talk-speakers/#numa
* https://netflixtechblog.com/serving-100-gbps-from-an-open-co...