Hej,
So, if you wanted to record your screen audio along with your screen you may have found the built in screen shot/recording tool lackluster.

Well it does not have to be, Apple should fix this but I’ll fix it for you instead.
This will be quick if you are of average competence.
Virtual audio driver
Well you’ll need to install a driver. You can use brew.
It’s called backhole 16 channel audio.
- It’s on brew : https://formulae.brew.sh/cask/blackhole-16ch
brew install --cask blackhole-16ch
Cool, once it is installed the next steps are just mucking about in settings.
Update Settings
Open Audio MIDI Setup from finder or however you open your apps.

Once open you need to add an aggregate device by clicking + bottom left.

F, I don’t see it in the list of Audio Devices

Restart your/my computer.
Works when you are back.
Tick BlackHole 16ch for your aggregate device.

Nice now add a Multi-Output Device.

If you use headphones turn them on already because this is kind of annoying.
So, you need to make sure Blackhole audio is at the bottom. Tick either just your headphones and then Blackhole 16ch or tick everywhere you want audio but make sure Blackhole 16ch is last. If you mess up you can untick everything and tick them agian.

If your Audio MIDI Setup looks kind of like the above then you are okay.
Final setup
The main idea is to use this new Multi-Output device when recording video.
Now open Settings and go to Sounds. Select the Multi-Output Device you just created.

Cool, now you can go record your video with the default recorder on Mac. Click Options and under Microphone select Aggregate Device.

The next video you record will have internal audio in it too.
Enjoy.