OK...this may read like a Fanboy post. Well...it’s not. However, I’ll leave that to your own interpretation 
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As you know the Sonos update to v13.4 brought DTS 5.1 Surround to Sonos home theaters speakers Arc and Beam Gen2. Since the update there have been posts complaining about DTS not being processed to the Arc. BTW the Beam Gen2 will process DTS as well; but the Arc seems to be the “whipping (boy) speaker”.
Fact of the matter is in addition to having a disc player that can decode the DTS signal and/or process DTS:HD to DTS your TV must be cable of “Pass-Through” audio to the Arc or Beam Gen2. If not you must consider using a HD Fury Acrana between your TV and Sonos speaker. To do so you split the incoming HDMI source signal to the FD Fury Acrana via HDMI-Out 1 to HDMI-In on the Arc or Beam; and HDMI-Out 2 to HDMI-In on the TV (*).
The point being is that Sonos delivered on their promise to bring DTS to the Arc and Beam. Albeit not DTS:HD or DTS:X. But nevertheless...DTS. If you are having difficulty getting DTS to Sonos the weak link is either the TV (i.e. no “Pass-Through” audio) and/or the inability of the disc player to process the DTS codec or downgrade DTS:HD to DTS.
(*) Use of HDMI 1 and 2 used only for visualization
For reference I’ve included how I was able to get DTS to the Arc and Beam Gen2. Also included are pics of the DTS signal being sent to both.
Disc: Alien 40 Anniversary / 4K Ultra HD Video / DTS:HD Audio
Sonos Equipment: Arc/Beam Gen2 with Sub x 2 and Sonos One x 2 / Sonos S2 app v13.4.
Transport: Panasonic DP-UB9000 Ultra 4K Blu-Ray Player > Audio Settings: DTS HD to DTS
Monitor: LG OLED 65 inch C9PUA > Audio settings: HDMI eArc / Pass-Through
