Reuters has a good page describing multiple secure ways to report a tip to them. Most reputable new sites with their stuff together will have a page like this and will use this software.
Signal is a good app for sending end-to-end encrypted messages. WhatsApp DOES NOT implement the same encryption algorithm, but they are owned by FACEBOOK and so therefore are not to be quite as trusted.
PGP is a method of encrypting email that only encrypts the content of the email, not the subject, email addresses, or names.