2G and 3G have been sunset in few countries and other countries will be sunsetting them soon. VoLTE feature of LTE modules is necessary to be able to do calls over 4G without 2G/3G fallback need.
Native SMS can be transmitted or received over 2G/3G circuit switched or packet switched. when 2G/3G are completely removed and we are left with 4G and 5G only. is the only way for SMS to continue is the use of IMS or are there any different solutions?
SMS can be sent over IMS using the IMS Core. If there is an existing LTE network but no IMS support, still the SMS can be sent or received over the SG interface in the LTE network.
Many operators use the SG interface to deliver and receive SMS.