Can I use
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Scoped attribute

- UNOFF

Deprecated method of allowing scoped CSS styles using a "scoped" attribute. Now removed from the specification and replaced by the @scope CSS rule.

Chrome

  1. ❌ 4 - 19: Not supported
  2. ❌ 20 - 36: Disabled by default
  3. ❌ 37 - 134: Not supported
  4. ❌ 135: Not supported
  5. ❌ 136 - 138: Not supported

Edge

  1. ❌ 12 - 134: Not supported
  2. ❌ 135: Not supported

Safari

  1. ❌ 3.1 - 18.3: Not supported
  2. ❌ 18.4: Not supported
  3. ❌ 18.5 - TP: Not supported

Firefox

  1. ❌ 2 - 20: Not supported
  2. ✅ 21 - 54: Supported
  3. ❌ 55 - 60: Disabled by default
  4. ❌ 61 - 136: Not supported
  5. ❌ 137: Not supported
  6. ❌ 138 - 140: Not supported

Opera

  1. ❌ 9 - 116: Not supported
  2. ❌ 117: Not supported

IE

  1. ❌ 5.5 - 10: Not supported
  2. ❌ 11: Not supported

Chrome for Android

  1. ❌ 135: Not supported

Safari on iOS

  1. ❌ 3.2 - 18.3: Not supported
  2. ❌ 18.4: Not supported
  3. ❌ 18.5: Not supported

Samsung Internet

  1. ❌ 4 - 26: Not supported
  2. ❌ 27: Not supported

Opera Mini

  1. ❌ all: Not supported

Opera Mobile

  1. ❌ 10 - 12.1: Not supported
  2. ❌ 80: Not supported

UC Browser for Android

  1. ❌ 15.5: Not supported

Android Browser

  1. ❌ 2.1 - 4.4.4: Not supported
  2. ❌ 135: Not supported

Firefox for Android

  1. ❌ 137: Not supported

QQ Browser

  1. ❌ 14.9: Not supported

Baidu Browser

  1. ❌ 13.52: Not supported

KaiOS Browser

  1. ✅ 2.5: Supported
  2. ❌ 3: Not supported
Resources:
Firefox bug #1291515: disable `<style scoped>` in content documents
HTML5Rocks article
Polyfill
HTML5 Doctor article