For some reason the only output audio devices I see in setting/system/audio are ALSA: AML-M8AUDIO, Analog and Pulse Bluetooth Audio. I would like to use ALSA: AML-M8AUDIO, HDMI or ALSA: AML-M8AUDIO, SPDIF but neither of them is listed. I think ALSA: AML-M8AUDIO, HDMI was used as default in the old tree. Using the new default ALSA: AML-M8AUDIO, Analog does not allow passthrough or at least 5.1 content is muted unless I keep the speaker settings to 2.0 (downmix apparently). My amp is connected via SPDIF. Passthrough is enabled both in audio settings and in the media properties.
In settings/player/video, sync player to screen is disabled. Adjust frame rate is also disabled.
Dmesg output is here: dmesg.txt.
System runs smoothly - very stable actually, better than v8.25.