2.1.8 only affects OS 3.0 and OSPi, it has not changed anything for OS 2.3. But don’t worry — this is NOT a sign that we are stopping support for OS 2.3 — this firmware is mainly aimed to fix some issues of OS 3.0 (by compiling the firmware with the latest ESP8266 WiFi library, and enabling support for expander 3.0 revision 1). Since these issues don’t apply to OS 2.3, this firmware has nothing to do with OS 2.3.