Hardware Acceleration on Chromium 99

Hi all,

I'm running chromium 99 on Bullseye:

Version 99.0.4844.51 (Official Build) built on Debian 11.2, running on Debian 11.2 (64-bit)

And I can't get hardware acceleration working. I've followed the instructions here:

https://wiki.debian.org/Chromium#Video_acceleration

As well as a variety of other online sources of increasingly dubious quality, so I've decided to come to the mailing lists and plea for help.

I'm running an Intel i5-5300U processor (so quite old I suppose):
- Intel(R) Core(TM) i5-5300U CPU @ 2.30GHz

with Intel Integrated graphics:
- Intel(R) HD Graphics 5500 (BDW GT2)

I've tried running it both with and without vulkan drivers enabled.

I'm runnin Vulkan Instance:
Vulkan Instance Version: 1.2.162

and some of the errors logs I'm getting particularly at startup look like this:

*** stack smashing detected ***: terminated
[32829:32829:0100/000000.428969:ERROR:sandbox_linux.cc(377)] InitializeSandbox() called with multiple threads in process gpu-process.
[32829:32829:0100/000000.432878:ERROR:vulkan_device_queue.cc(227)] Vulkan: Intel(R) HD Graphics 5500 (BDW GT2)

I'm checking to see if hardware accelerated video decoding is working by viewing this video in 1080p HD:
https://www.youtube.com/watch?v=HmZKgaHa3Fg

and looking at the output of intel_gpu_top, where the row for Video/0 stays at 0%.

Anyone got any ideas?

- Kevin