Build Mesa.  The usual procedure to build. For options something like

    meson setup -Dgallium-drivers=asahi -Dvulkan-drivers=

We learned the hard way that disabling gles1 also disables conformance. This
may be a CTS bug, but distros should be shipping gles1 support anyhow.

Build the conformance tests. This can take quite a bit of time (and RAM) even
on apple silicon, consider doing it on your fastest machine. Do so exactly as
documented here. Do not reuse your existing clone/build.

    $ git clone https://github.com/KhronosGroup/VK-GL-CTS.git -b opengl-es-cts-3.2.9.3
    $ cd  VK-GL-CTS
    $ python3 external/fetch_sources.py
    $ cd ..
    $ mkdir build
    $ cd build
    $ cmake ../VK-GL-CTS/ -DDEQP_TARGET=x11_egl -GNinja -DCMAKE_BUILD_TYPE=Release
    $ ninja

Copy the resulting build/ directory to each system you're running the CTS on.

On each system:

    $ cd build/external/openglcts/modules/
    $ ./cts-runner --type=es31

This will take a LONG time but should finally declare the implementation conformant. If so, run

    $ cd VK-GL-CTS
    $ git status > ../git-status.txt
    $ git log --first-parent  opengl-es-cts-3.2.9.3^..HEAD > ../git-log.txt
    $ cd ..
    $ zip for-alyssa.zip build/external/openglcts/modules/*.qpa build/external/openglcts/modules/cts-run-summary.xml git-status.txt git-log.txt

Run exactly as written here. Do not e.g. copy-paste the git log from stdout.
That will fail conformance. We also learned this one the hard way.

Do not > into the same directory as the CTS. This will probably also fail
conformance.

Send me the resulting for-alyssa.zip (it will be large) along with which system
this ran against and I'll take care of the rest.

If this fails, let me know and I'll advise how to proceed.

Source: https://github.com/KhronosGroup/VK-GL-CTS/wiki/Creating-a-OpenGL-and-OpenGL-ES-Submission-Package