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SMS is standard on any device that does not have a supporting Android phone, using a basic phone, or a KaiOS phone. As with GSMA version of RCS, encryption is not supported in any form with SMS. SMS is limited to 160 characters for SMS length. If the number of SMS messages sent is important to you, keep in mind of this 160 character limit. If you send a 161 character SMS message, it would count as 2 SMS messages. This is a flaw with SMS, and one of the reasons RCS and iMessage is so much more preferred.
If you are using a basic phone or a KaiOS phone, your only option is SMS. This is due to the flaw of the device OS, and the fact that KaiOS, or basic phones can not install software that will give them additional support for other platforms. If you are opposed to using SMS, you must acquire a supporting smartphone. The only Android phone I know that does not support RCS will be Graphene OS. If you are buying a smartphone because you want better than SMS options, stay away from Graphene OS as an option.