Hello @pavelrz, welcome to the Sonos Community!
I am sorry to hear you are experiencing issues getting your Sonos Home Theater setup to produce 5.1 audio via your Nintendo Switch 2 console.
When it comes to gaming consoles and Sonos, the Sonos soundbars simply play the audio format that they receive from the TV, and since you have no issues with your Sony PS5 or Nintendo Switch 1, that makes me think it’s relative to the newly released Nintendo Switch 2.
I would suggest you to disable the Nintendo Switch 2 System Virtual Surround setting, if it’s enabled, and see if that makes a difference. We don’t really want the console to configure the audio to that extend.
Another thing you could do is Submit Diagnostics while your Nintendo Switch 2 is playing audio via your Sonos HT and contact our Support Team for live troubleshooting.
They have tools at their disposal to provide you with information and advice specific to your Sonos system and what it reports.
I hope this helps.