Signal is an open-source privacy-focused end-to-end encrypted texting platform (so competing with SMS, WhatsApp, iMessage, Telegram, and similar). It’s developed by a donation-funded non-profit organization.
Signal is quite good compared to the competition, but it faces a lot of scrutiny because they make big promises about privacy and security so the people who care will really get into the details on that. Also IIRC there was a period when one of their competitors was trying to slander them more or less.
In general there’s nothing wrong with Signal and it’s quite a good option. If you really care about the privacy details you can always host your own instance (but that would require you to convince your friends to use your instance … it’s not federated).
Star Wars and Star Trek are really tangential fandoms except for the intersection in the name.