PROOF OF CONCEPT: Securely Erase SSD Data? !! READ THE DESCRIPTION !!
5Disclaimer: YOU SHOULD NOT erase your SSD like this because it may not achieve the goal (cut from diskutil's manual at the end).
The best method is to encrypt your data and "forget the password". This is only shown as proof of concept.
There is software offered by the manufacturers, like: Seagate SeaTools, Western Digital SSD Dashboard or Samsung Magician. I did not test those and probably will not. However, in conclusion, you want to know how to keep your data secure on SSD? ENCRYPT IT! ;)
NOTE from "man diskutil" regarding secureErase and SSD:
This kind of secure erase is no longer considered safe. Modern devices have wear-leveling, block-sparing, and possibly-persistent cache hardware, which cannot be completely erased by these commands. The modern solution for quickly and securely erasing your data is encryption. Strongly-encrypted data can be instantly "erased" by destroying (or losing) the key (password), because this renders your data irretrievable in practical terms. Consider using APFS encryption (FileVault).