I just tested this on my AMD box featuring
Athlon X4 845 and dual GPUs
VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti XT [Radeon HD 7970/8970 OEM / R9 280X].
I downloaded the snap as instructed and performed the test on
4.13.0-16-generic using snapd
2.30~rc1 on a Ubuntu 17.10 host.
I tried a few movies on my disk and I saw this printed on the console:
[00007f782801a800] avcodec decoder: Using G3DVL VDPAU Driver Shared Library version 1.0 for hardware decoding
I dragged the display from one GPU to another (they are connected to separate monitors) and it all worked without any issues. Audio was working flawlessly as well.