Update (or install) Ungoogled Chromium (ARM64 / Apple "M1") with Widevine.

update-chromium.mjs

#!/usr/bin/env zx

const fs = require('fs')

async function getCurrentVersion() {
  let version;

  try {
    version = await $`/Applications/Chromium.app/Contents/MacOS/Chromium --version`
  } catch (e) {
    return null
  }

  if (version && version.stdout.indexOf('Chromium ') === 0) {
    return version.stdout.split(' ')[1]
  }
}

async function getLatestRelease() {
  const response = await fetch('https://api.github.com/repos/ungoogled-software/ungoogled-chromium-macos/releases')
  const releases = await response.json()

  return releases.flatMap(release => release.assets || {})
    .filter(asset => asset.name?.endsWith('_arm64-macos.dmg'))
    .find((release) => release?.browser_download_url && release?.name)
}

async function installUngoogledChromium(downloadUrl) {
  await $`curl -L -o ungoogled-chromium.dmg -O ${downloadUrl}`
  await $`hdiutil attach ungoogled-chromium.dmg`

  if (fs.existsSync('/Applications/Chromium.app')) {
    await $`killall "Chromium" || true`
    await $`rm -r /Applications/Chromium.app`
  }
  await $`cp -R /Volumes/Chromium/Chromium.app /Applications`

  await $`sleep 1` // Workaround for 'hdiutil: couldn't unmount "diskX" - Resource busy'
  await $`hdiutil detach "/Volumes/Chromium/"`
  await $`rm ungoogled-chromium.dmg`
}

async function patchWidevineSupport() {
  await $`curl -O https://dl.google.com/chrome/mac/universal/stable/GGRO/googlechrome.dmg`
  await $`hdiutil attach googlechrome.dmg`

  let src = '/Volumes/Google Chrome/Google Chrome.app/Contents/Frameworks/Google Chrome Framework.framework/Libraries/WidevineCdm'
  let dest = '/Applications/Chromium.app/Contents/Frameworks/Chromium Framework.framework/Libraries/'
  await $`cp -R ${src} ${dest}`

  await $`sleep 1` // Workaround for 'hdiutil: couldn't unmount "diskX" - Resource busy'
  await $`hdiutil detach "/Volumes/Google Chrome/"`
  await $`rm googlechrome.dmg`
}

const currentVersion = await getCurrentVersion()
const latestRelease = await getLatestRelease()

if (currentVersion && latestRelease.name.indexOf(currentVersion) > -1) {
  console.log('Already up to date')
  process.exit(0)
}

cd('/tmp')
await installUngoogledChromium(latestRelease.browser_download_url)
await patchWidevineSupport()
await $`open /Applications/Chromium.app`

Superseded by https://github.com/claudiodekker/chromium-update-notifier