Update, June 22, 2020: Mixer closing
Microsoft announced that it would be discontinuing the Mixer streaming service. It would also be teaming up with Facebook Gaming to provide a potential partnership for exclusive Mixer streamers.
Best answer: Unfortunately, there is no native Mixer app on the PlayStation 4, meaning you'll have to watch from your phone or computer if you happen to want to watch a stream. However, there are workarounds to streaming from a PlayStation 4, if that's somehow you're looking to accomplish.
A solid workaround: Elgato Game Capture 4K60 Pro ($250 at Amazon)
Using Mixer on PlayStation 4
With many streamers in today's world usually choosing a side between Mixer and Twitch, it creates a bit of a challenge for audiences looking to watch their favorite content creators. Unfortunately for PlayStation 4 users, if they want to watch their favorite streamers on Mixer, they'll have to do it without a PS4.
https://twitter.com/watchmixer/status/987383138606297088?lang=en
As of now, there is no native application for Mixer on PlayStation 4 like there is for Twitch. This is likely due to Mixer being funded and developed by Microsoft, although Mixer has stated in the past that they would love to see an app come to PlayStation 4 at some point in the future. There are some workarounds, like navigating to Mixer's website via the PlayStation 4 web browser, but it's probably much easier to just watch a stream on your computer or phone if you're looking to do that.
How to stream PlayStation 4 to Mixer
While some people may just want to watch a stream or two on PlayStation 4, some players also want to be able to stream from the console itself to the streaming platform. Because there's no native application for Mixer on PlayStation 4, players can't simply press the Share button on their controller and stream like they can to Twitch or YouTube. However, there's some workarounds to this that involve typical streaming tools.
https://twitter.com/WatchMixer/status/1038193698104852480
According to Mixer back in 2018, streaming from a PlayStation 4 to Mixer is as simple as using a capture card or the PlayStation Remote Play App, connecting to a PC, and broadcasting the stream normally. Of course, this requires a bit more complex of a setup, as its necessary to have a PC capable of broadcasting a stream as well as keeping everything stable throughout. Unfortunately, this seems to be the only way to reliably stream from a PlayStation 4 to Mixer, although Mixer has said that they will continue to look into getting the streaming app on more platforms in the future.
Capture your games fully
The Elgato 4K60 Pro is the best of the best and will capture games in full 4K60FPS with ultra-low latency, which is exactly what you'll need if you want to level up as a streamer.
