I've been grabbing macOS builds of Chromium from the Playwright project (https://playwright.dev)

The download URL follows this template

    https://playwright.azureedge.net/builds/chromium/{revision}/chromium-mac.zip

To find the current revision, look in

    https://raw.githubusercontent.com/microsoft/playwright/main/packages/playwright-core/browsers.json

Today I'm seeing

    {
      "name": "chromium",
      "revision": "1151",
      "installByDefault": true,
      "browserVersion": "132.0.6834.32"
    },

So I'd grab

    https://playwright.azureedge.net/builds/chromium/1151/chromium-mac.zip

After unzipping, mark the file as runnable with

    xattr -d com.apple.quarantine Chromium.app