Helpful on my M31s. First time root was working on it's own. Second time had to delete the services mentioned form /system/app as well as priv-app.Still doesn't work for me. (My device is snapdragon)
In some telegram groups, I heard that some people got secure folder fixed, by removing Knox related apps. Maybe you could check out that solution?
Edit: So I checked the groups out to make sure, and people said they deleted all knox apps inside system/app and system/priv-app but only left KnoxGuard remaining
And this should fix securefolder without any patches
edit - Has now stoppped working. Had upgraded to ONE UI 4.1.