XHTML served as application/xhtml+xml

- LS

A strict form of HTML, and allows embedding of other XML languages

Chrome

  1. 4 - 121: Supported
  2. 122: Supported
  3. 123 - 125: Supported

Edge

  1. 12 - 121: Supported
  2. 122: Supported

Safari

  1. 3.1 - 17.2: Supported
  2. 17.3: Supported
  3. 17.4 - TP: Supported

Firefox

  1. 2 - 122: Supported
  2. 123: Supported
  3. 124 - 126: Supported

Opera

  1. 9 - 105: Supported
  2. 106: Supported

IE

  1. 5.5 - 8: Not supported
  2. 9 - 10: Supported
  3. 11: Supported

Chrome for Android

  1. 122: Supported

Safari on iOS

  1. 3.2 - 17.2: Supported
  2. 17.3: Supported
  3. 17.4: Supported

Samsung Internet

  1. 4 - 22: Supported
  2. 23: Supported

Opera Mini

  1. all: Supported

Opera Mobile

  1. 10 - 12.1: Supported
  2. 73: Supported

UC Browser for Android

  1. 15.5: Supported

Android Browser

  1. 2.1 - 4.4.4: Supported
  2. 122: Supported

Firefox for Android

  1. 123: Supported

QQ Browser

  1. 13.1: Supported

Baidu Browser

  1. 13.18: Supported

KaiOS Browser

  1. 2.5: Supported
  2. 3: Supported

The XHTML syntax is very close to HTML, and thus is almost always (incorrectly) served as text/html on the web.

Resources:
Information on XHTML5
Wikipedia
Sub-features:
XHTML+SMIL animation