Every S series and the better A series phones. An a5x phone usually will have it but with A series phones it's not guaranteed which ones do. All S series do, most good A series do. The folds and flips do too of course
Go to settings, security and privacy, more security settings, secure folder. If the secure folder button isn't there, it doesn't have it. Another tell, if during boot the phone says "secured by knox" then decent chance it has secure folder
All the current generation A series phones have Secure folder. The Device needs to have the full one Ui software and not One UI core. Aditionally the device must be running Android 7 and above. Not the most modern article but differences explained here
