At least 5.1, e.g. when using the TVs internal Netflix app. I will do some poking today to see if there are any quirks that could affect this possible use case.
Further to this, I have been testing use cases with my TV using eARC. ATMOS turned off and AVR set to straight decode of the input.
For all sources internal to the TV, it works great, i.e. eARC digital audio out "auto mode" produces multichannel PCM to the AVR, even if sources are DD or DD+.
For sources external to the TV, things are a bit different:
Using an Oppo BDP-93 player, "Screamadelica Live" bluray which has DTS-HD master audio 5.1, DD 5.1, LPCM 2.0, with the Oppo left in "BItstream" audio output over HDMI:
- The TV digout mode of "passthrough" decodes DTS to LPCM 5.1, DD is passthrough to DD 5.1, PCM is passthrough to PCM 2.0.
- The TV digout mode of "AUTO" downmixes all to PCM 2.0
- The TV digout mode of "PCM" downmixes all to PCM 2.0
With the Oppo set to LPCM out over HDMI instead:
- The TV digout mode of "passthrough" source DTS produces PCM 5.1 at AVR, source DD produces PCM 5.1 at AVR, source PCM produces PCM 2.0 at AVR
- The TV digout mode of "AUTO" downmixes all to PCM 2.0
- The tV digout mode of "PCM" downmixes all to PCM 2.0
The conclusion is for my Samsung TV (2021 QLED) is that, if you want to get MC PCM out of it, internal sources are fine, external DTS is fine, but to get external DD to MC PCM requires use to do the decoding in the external source.
I'm not sure why the TV decodes DTS for the passthrough case, as the AVR does support the decoding of it! The result was the same regardless if the AVR was in DTS mode 1 (normal) or mode 2 (if input was not producing DTS HD properly)
I hope this was useful to someone considering the Flex HT with a Samsung TV using eARC. Of course, the Flex HT may not present the same audio decode options to the TV in handshaking so actual results with it may be different.