Step 1: Launch Streamlabs
Open the Streamlabs application on your computer. If you don't have Streamlabs installed, you can download it for free from the official website: https://streamlabs.com/
Step 2: Access Streamlabs settings
In the lower-left corner of the Streamlabs window, click on the "Settings" button (the cog-icon) to open the Settings window.

Streamlabs settings
Step 3: Go to the 'Output' Settings
In the Settings window, click on the "Output" tab located on the left-hand side.
Step 4: Switch to 'Advanced' Output Mode
In the "Output" tab, locate the "Output Mode" dropdown menu. By default, it's set to "Simple." Click on the dropdown menu and select "Advanced" to access advanced output settings.

Streamlabs Output Mode selection
Step 5: Navigate to the 'Recording' Settings
Once you've switched to "Advanced" output mode, you'll see four tabs under the "Output" settings: "Streaming", "Recording", "Audio" and "Replay Buffer". Click on the "Recording" tab.
Step 6: Select the h264 (x264) Encoder
In the "Recording" tab, find the "Encoder" dropdown menu. Click on it and select "x264" from the available options. This is the h264 encoder.

Streamlabs Recording encoder
Step 7: Configure Additional Settings (Optional)
While you're in the "Recording" tab, you can also configure additional settings, such as the recording path, recording format, and custom Muxer settings. Adjust these settings as needed, based on your preferences and requirements.
Step 8: Save Your Settings
After selecting the h264 (x264) encoder and configuring any additional settings, click on the "OK" button in the lower-right corner of the Settings window to save your changes.
Step 9: Start recording
Now that you have set the recording output encoder to h264 (x264), you can start recording your videos in Streamlabs. To begin recording, click on the "Start Recording" button located in the lower-right corner of the Streamlabs window.
Conclusion
By following these steps, you can successfully set the Streamlabs recording output encoder to h264 (x264), ensuring compatibility with tools like StreamLadder and providing a smooth viewing experience for your audience. Happy streaming!