There’s no filter for filtering all of the HTML output in the admin. The closest thing is the gettext
filter:
function wpse_275812_filter_text( $translated_text, $text, $domain ) {
$translate_text = str_ireplace( 'foo', 'bar', $translated_text );
return $translated_text;
}
add_filter( 'gettext', 'wpse_275812_filter_text' );
This filters any text output by the internationalization functions (__()
, _e()
, etc.). So it will only work if the plugin you’re trying to filter uses these functions to output its text.
If it doesn’t, there’s nothing you can really do.