https://github.com/qmk/qmk_firmware/pull/24560#discussion_r1893059336

common/keymap.h

@@ -96,6 +96,17 @@ char chordal_hold_handedness(keypos_t key)
     return (key.row < MATRIX_ROWS / 2) ? 'L' : 'R';
 }
 
+bool get_chordal_hold(uint16_t tap_hold_keycode, keyrecord_t* tap_hold_record,
+                      uint16_t other_keycode, keyrecord_t* other_record) {
+    // Allow hold between any pair of mod-tap keys.
+    if (IS_QK_MOD_TAP(tap_hold_keycode) && IS_QK_MOD_TAP(other_keycode)) {
+        return true;
+    }
+
+    // Otherwise defer to the opposite hands rule.
+    return get_chordal_hold_default(tap_hold_record, other_record);
+}
+
 #ifndef CC_NO_LED
 
 void keyboard_post_init_user(void) {