If your TV can pass through Atmos, as proven by the Fire stick. I’m curious why it would not do the exact same thing from the PS5 - if you do not know why, are you sure the device you chose will help?

It may send eArc directly to the Arc so it can play Atmos. 

I really don't know why the Fire Tv sends Atmos and the PS5 doesn't =(

@Thrash 

What kind of signal do Sonos app show from ps5? And what kind of content are you playing on ps5? I‘m with @106rallye and think it’s possible in generell with your tv with a least compressed Atmos because Fire TV works. 
Has your TV ARC or eARC connection? Just to check if it can be used also with uncompressed Atmos. And you can check ps5 audio settings and the content you play on ps5. Often there is no Atmos audio track but just multichannel pcm. 

Thanks for your help! 

I have everything configured for Dolby Atmos but all I get is Dolby Digital Plus 5.1. I don't know why! I have Arc, but I do get compressed Atmos through the Fire TV. I've tried everything but I just can't get Atmos to work =(

Maybe the PS5 only does uncompressed Atmos? And your TV does not do passthrough on uncompressed Atmos streams because it does not have an eARC connection?

Have you proven that the PS5 can send ATMOS directly to ARC?

No I haven't! I think that may be it. Ps5 doesn't send compressed Atmos! Will the device I posted work then? O_o

Would have been helpful if you had answered the questions like if your tv supports eARC or just ARC. 
Anyway the device you mentioned would have to support an hdmi eARC INPUT for Sonos Arc and at least one standard hdmi in and one out. 

Mi TV only has ARC out but it does output Atmos from Fire TV. 

So that‘s the point… ps5 also like AppleTV uses Dolby MAT. And that needs an eARC connection to work with uncompressed Atmos. 
Your Fire TV uses compressed DD+ Atmos and that works with ARC. 

Ooooh PS5 is uncompressed? That's it. So the device that I posted can help?? 

As I said before you have to check if it supports the necessary hdmi connections I mentioned above. 
I won‘t open an unknown https link posted here.

Oh, understood. It's this one. Here are the specs:

Specification:

※Mode Name:HDMI eARC/ARC Audio Extractor

※Input channel:HDMI port x1

※Output channel:HDMI port x2,RCA port x2,Optical port x1

※eARC features:Support Optical,L/R,HDMI OUT2 output

※ARC features:Support Optical,L/R,HDMI OUT2 output

※Video format:HDR,UHD,HLG,Dolby Vision

※Resolution format:480P/720P/1080P/4K@30Hz/4K@60Hz

※Deep color:8/10/12Bit@480P/720P/1080P 8Bit@2160P

※HDMI In/Out Supported Audio Format:Dolby HD/DTS HD/Dolby Atoms/Dolby AC3/DTS/LPCM etc.

※Digital audio output supported audio format:LPCM2.0/DTS/DOLBY-AC3……

※HDMI Input cable length:2160P/AWG 26 ≤3m;1080P/AWG 26 ≤10m

※HDMI Output cable length:2160P/AWG 26 ≤3m;1080P/AWG 26 ≤10m

※DAC sample frequency range:32～192 KHz

※HDMI transmission bandwidth:25~600MHz

※HDMI transmission rate:0.75~18Gbps

※P specification: Input: AC 100~240V Output: DC 5V/1A

※Max working current:600mA

※Size:139x64.5x22.3 (mm)

※Weight:225g

※Accessories:Manual, Power Adaptor

@Thrash 

As expected this device has NO hdmi INPUT that supports eARC. 
So it WON‘T work for you. 

Really? 

I though "HDMI In/Out Supported Audio Format:Dolby HD/DTS HD/Dolby Atoms/Dolby AC3/DTS/LPCM etc." meant it supported it =(

Once again… to connect a Sonos ht device  you need a hdmi in port that supports eARC. The linked device hasn’t got one.