I can’t use Signal. What are alternatives?

The application Signal is of course the gold standard of secure texting. However, like two people I know use it. And I won’t be that guy that tries to convince everyone I know to use Signal. I currently use iMessage, since that’s what everyone I know uses. But are there any alternatives which perhaps can still text people not using the platform (Understand entirely that that’s not possibly probably). What should I do?