Hi @PaulinBont,
Thanks for reaching out to the Sonos community and for letting us know about your concern. Let me share with you about the Sonos Arc.
The Sonos Arc can play Dolby Atmos audio. ARC and eARC are protocols responsible for sending audio over an HDMI cable to home theater sound systems like Sonos Arc. Sonos Arc must be connected to HDMI ARC or HDMI eARC to play any Dolby Atmos content. Not all TVs have HDMI ARC or HDMI eARC. Your Sony TV AF9 has HDMI and HDMI ARC.
Getting Dolby Atmos audio can also depend on the TV and the format or output must be set to one of our supported home theater audio formats. Some TV and movie streaming services now support Dolby Atmos. Please note that even if a service supports Dolby Atmos, some shows and movies may not have Dolby Atmos audio. Check with your streaming service provider to see if they support Dolby Atmos.
Let me share this community thread that might help you out. We can wait for suggestions and feedback from our Sonos community members, they might provide their opinion about this.
Please let me know if you have any further questions or concerns, I'll be glad to assist you.