I stream netflix, the movie Gravity..

Still I see stereo input ;(

I don't seem to get this info on; input 5.1

The way I've setup:

Sonos amp + surround speakers.

Connected via HDMI to Panasonic tv.  → TV detects home surround system.

Chromecast streams movies on the panasonic, and chromecast can auto detect surround sound.

Still it says audio in stereo pcm..

Who can help me? :)

Surely you need a Beam or Arc? The Amp is a stereo device, as is a pair of One SL’s. 

Thats not true.. the sonos amp can do surround too! 

You can even attach a subwoofer to the Sonos amp if needed..

You are correct that you can the amp is capable of dolby digital 5.1.  It cannot do dolby digital plus, True HD, or DTS flavors though.  I would verify your source content.  Also, I would verify that your chromcast is actually sending audio in DD 5.1 even if the source is capable.  I honestly don’t know much about chromecast since I don’t use it myself, but would not be surprised if it’s limited to stereo if your streaming content wirelessly, or something of that nature.  If you have something else besides chromecast, you could test that out.

Can I connect my laptop to the tv and then play a file from these websites:

https://thedigitaltheater.com/dolby-trailers/

Or does a laptop also only sent stereo?

I must say that when I play a test from the website, the sound comes from the backspeakers as intented.

I've read somewhere some tv outputs call it PCM Stereo -> which can be surround.. What do you think?

Anyone? :)