https://wccftech.com/google-chrome-os-flex-turns-your-old-mac-into-a-working-machine/

If you currently own an older Mac that is unable to run the latest macOS update, instead of discarding the machine and adding to the already high e-waste counter, you can use Google’s Chrome OS Flex to re-purpose it. Google’s latest endeavor gives early access to users and a chance to revive their old hardware instead of throwing it away.

Google claims that replacing an existing operating system with Chrome OS Flex will take a matter of minutes. The company has also provided details on its website on how to start running the OS on older machines, with the steps to install it given below.