How should I enable hardware graphics acceleration in Chromium web-browser running on Ubuntu MATE 21.10 on RPi 4 (armhf)?

I have just installed Ubuntu MATE 21.10 (32-bit, armhf) on my Raspberry Pi 4 with 4 Gb of RAM. Note: I need 32-bit version to have Modelica compiler available. All settings are default. Information about video driver is below:

$ lsmod | grep drm
drm_kms_helper        282624  3 vc4
cec                    65536  2 vc4,drm_kms_helper
fb_sys_fops            16384  1 drm_kms_helper
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
drm                   540672  12 v3d,vc4,gpu_sched,drm_kms_helper

$ grep -E "^dtoverlay|^max_framebuffers|^gpu_mem|^hdmi" /boot/firmware/config.txt 
max_framebuffers=2
dtoverlay=vc4-fkms-v3d
gpu_mem=128

$ cat /proc/device-tree/soc/firmwarekms@7e600000/status
okay

$ cat /proc/device-tree/v3dbus/v3d@7ec04000/status
okay

$ glxinfo | grep -i opengl
OpenGL vendor string: Broadcom
OpenGL renderer string: V3D 4.2
OpenGL version string: 2.1 Mesa 21.2.2
OpenGL shading language version string: 1.20
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.1 Mesa 21.2.2
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.10
OpenGL ES profile extensions:

Then I installed Chromium browser as simple as sudo apt-get install chromium-browser, launched it for first time to enable the following options on chrome://flags:

• Override software rendering list aka #ignore-gpu-blocklist;
• GPU rasterization aka #enable-gpu-rasterization;
• Zero-copy rasterizer aka #enable-zero-copy;
• Enables Display Compositor to use a new gpu thread. aka #enable-drdc;
• Out-of-process 2D canvas rasterization. aka #canvas-oop-rasterization.

then relaunched it using chromium --enable-features=VaapiVideoDecoder command.

Desite all these steps done, on chrome://gpu Chromium says that GPU acceleration is not enabled:

Graphics Feature Status

• Canvas: Software only. Hardware acceleration disabled
• Canvas out-of-process rasterization: Disabled
• Compositing: Software only. Hardware acceleration disabled
• Multiple Raster Threads: Disabled
• Out-of-process Rasterization: Disabled
• OpenGL: Disabled
• Rasterization: Software only. Hardware acceleration disabled
• Raw Draw: Disabled
• Skia Renderer: Enabled
• Video Decode: Software only. Hardware acceleration disabled
• Vulkan: Disabled
• WebGL: Disabled
• WebGL2: Disabled

So the question is in the title.

>Solution :

The main problem here is that Chromium is shipped as Snap, so VA-API is not available as we are running on ARM.

So the first step is obvious – remove Snap version of Chromium by sudo snap remove chromium.

The second step is installation of Chromium as deb-package from RaspberryPi OS repository using below commands:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 82B129927FA3303E
sudo apt-add-repository "deb http://archive.raspberrypi.org/debian/ bullseye main"

cat <<EOF | sudo tee /etc/apt/preferences.d/pin-chromium
Package: *
Pin: release o=Raspberry Pi Foundation
Pin-Priority: -1

Package: chromium*
Pin: release o=Raspberry Pi Foundation
Pin-Priority: 1000
EOF

sudo apt-get update
sudo apt-get install chromium-browser

Then launch Chromium to configure it as usual – enable the following options on chrome://flags:

• Override software rendering list aka #ignore-gpu-blocklist;
• GPU rasterization aka #enable-gpu-rasterization;
• Zero-copy rasterizer aka #enable-zero-copy;
• Enables Display Compositor to use a new gpu thread. aka #enable-drdc;
• Out-of-process 2D canvas rasterization. aka #canvas-oop-rasterization.

Relaunch it using chromium-browser --enable-features=VaapiVideoDecoder, visit chrome://gpu to ensure that you have all (excluding Vulkan) options enabled:

Graphics Feature Status

• Canvas: Hardware accelerated
• Canvas out-of-process rasterization: Enabled
• Compositing: Hardware accelerated
• Multiple Raster Threads: Enabled
• Out-of-process Rasterization: Hardware accelerated
• OpenGL: Enabled
• Rasterization: Hardware accelerated on all pages
• Skia Renderer: Enabled
• Video Decode: Hardware accelerated
• Vulkan: Disabled
• WebGL: Hardware accelerated
• WebGL2: Hardware accelerated

To make --enable-features=VaapiVideoDecoder flag permanent one should edit the relevant config-file programmatically as shown below:

echo 'CHROMIUM_FLAGS="${CHROMIUM_FLAGS} --enable-features=VaapiVideoDecoder"' | sudo tee /etc/chromium.d/92-vaapi-hardware-decoding

As the result all web-players will play 1080p without lags and tearing.