I suggest dropping the MacOS and installing Linux. You can make Linux a fit for purpose operating system that focuses on streaming. Even an older device is plenty fast given the right configuration. That is pretty much what every commercial streamer is anyway.
Below is an AI summary of the install process. This is a link explaining how to build the device for streaming. I have done this with a very humble Dell E6510 and is does quite well. Albeit I don't stream a lot, but when I do I am not disappointed in the results.
https://www.24bit96.com/hifi-music-server/bitperfect-linux-with-mpd.html
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Installing Linux on a 2012 MacBook Pro is possible and can be a good way to give the older machine new life, especially if you're looking for a more lightweight and efficient operating system. It involves creating a bootable USB drive with a Linux distribution, booting from the USB, and then installing the chosen distribution. However, you may need to install drivers for Wi-Fi and other hardware.
- Choose a Linux Distribution: Consider options like Ubuntu, Linux Mint, Pop!_OS, or EndeavourOS. Ubuntu and its derivatives are often recommended for beginners.
- Download the ISO Image: Get the ISO file for your chosen distribution from its official website.
- Create a Bootable USB Drive: Use a tool like Rufus or Etcher to write the ISO to a USB drive.
- Boot from the USB: Shut down the MacBook Pro, insert the USB drive, and then power it on while holding down the Option (Alt) key until the Startup Manager appears.
- Select the Bootable USB: Choose the USB drive from the Startup Manager icons.
- Follow the Installation Instructions: The Linux installer will guide you through the installation process, including partitioning the hard drive.
- Install Drivers: You may need to install drivers for Wi-Fi (Broadcom drivers are common on 2012 MacBook Pros) and other hardware after the initial installation.