On a MW 1.39 installation (1.39.5. PHP 7.4.33, CodeMirror 4.0) I see the follwing deprecation notice:
2023/12/18 14:48:08 [error] 22051#22051: *41089 FastCGI sent in stderr: "PHP message: PHP Deprecated: Use of User::getOption was deprecated in MediaWiki 1.35. [Called from CodeMirrorHooks::isCodeMirrorOnPage in extensions/CodeMirror/includes/CodeMirrorHooks.php at line 20] in includes/debug/MWDebug.php on line 381PHP message: PHP Stack trace:PHP message: PHP 1. {main}() index.php:0PHP message: PHP 2. wfIndexMain() index.php:46PHP message: PHP 3. MediaWiki->run() index.php:50PHP message: PHP 4. MediaWiki->main() includes/MediaWiki.php:562PHP message: PHP 5. OutputPage->output() includes/MediaWiki.php:922PHP message: PHP 6. MediaWiki\HookContainer\HookRunner->onBeforePageDisplay() includes/OutputPage.php:2871PHP message: PHP 7. MediaWiki\HookContainer\HookContainer->run() includes/HookContainer/HookRunner.php:946PHP message: PHP 8. MediaWiki\HookContainer\HookContainer->callLegacyHook() includes/HookContainer/HookContainer.php:137PHP message: PHP 9. CodeMirrorHooks::onBeforePageDisplay() includes/HookContainer/HookContainer.php:338PHP message: PHP 10. CodeMirrorHooks::isCodeMirrorOnPage() extensions/CodeMirror/includes/CodeMirrorHooks.php:38PHP message: PHP 11. User->getOption() extensions/CodeMirror/includes/CodeMirrorHooks.php:20PHP message: PHP 12. wfDeprecated() includes/user/User.php:2123PHP message: PHP 13. MWDebug::deprecated() includes/GlobalFunctions.php:765PHP message: PHP 14. MWDebug::deprecatedMsg() includes/debug/MWDebug.php:233PHP message: PHP 15. MWDebug::sendRawDeprecated() includes/debug/MWDebug.php:352PHP message: PHP 16. trigger_error() includes/