I've noticed occasional audio dropouts during movies, but there are no traces of anything in Kodi or ffmpeg logs and the event is not reproducable, e.g. rewind media and the event does not reoccur at the same point. I have no idea how to reproduce or debug this so it's something I need to flag to upstream devs. I have a hunch (based on similar issues with Amlogic hardware) that this is related to unstable clocks, but I have no way to prove that and I have low expectations of an easy find or fix.
I've not experimented much with 192KHz audio. If you have some structured test media that you can share, send me a download link; email to chewitt@ our domain or Kodi domain.
I've not seen dropped frames in videos other than some known-bad test media with exotic/problem encodings, but playback is sensitive to using correct modes so I would strongly advise everyone to use adjust-refresh and the general config outlined in this wiki article: https://wiki.libreelec.tv/configuration/4k-hdr
The kernel DRM layer is using HDMI 2.0/2.1 mode timings which are standards and both LE and Armbian are broadly using the same versions of mesa/panfrost, although this is only relevant for rendering the Kodi GUI an has nothing to do with HDMI modes and DRM connector timings. The one possible difference between LE and Armbian is that I have a bunch of in-flight patch series that enable deep-colour and HDMI 2.1 capabilities in the kernel and Armbian probably doesn't. That's all going to be merged upstream at some point though, and it's still the AVR's responsibility to generate its own OSD and overlay this onto the HDMI signal sent to the TV so if it can pass HDMI video/audio but not show its own OSD that sounds like an AVR bug. FWIW, the OSD of my 2018-ish Marantz AVR shows up fine on the rare occasions I display it.
There are lots of in-flight patch series required for the image. All current hardware decode ones are included.