vvdec is not free software, and is not open source under the definition. Its license expressly withholds patent rights. This means it will never get used in VLC or FFmpeg, or at least it will never get distributed with it.
I'm trying to get VLC to play AAC 5.1 surround encoded MKV's but it just plays through stereo. I have confirmed it does work with some DTS test file I downloaded. I'm on linux with SPDIF output using ALSA output over Playback through PulseAudio. Does VLC even support AAC surround?