I had the same happen when upgraded to the Samsung S20 plus. Lost everything!. Secure folder failed via Smart Switch, Samsung Cloud backup, Google cloud backup and even SD card backup!. Got a message saying Secure Folder wasn't supported although it's on the phone and I can access it with my pin. Luckily for me, being one step ahead always, in case, I had also backed up everything within my secure folder onto my PC and so was able to manually replace all the lost data/text, very important stuff I need, only I cannot trust Secure Folder after this and so my data is instead in basic Samsung notes which makes me uneasy.
