In good old days, up to 30 images could be selected directly in the background settings, which were then randomly set as a lock screen image. Unfortunately, this option has been denied to us by Samsung, now it is only possible with live wallpapers, which are often paid, and we cannot choose the pictures ourselves.
Fortunately, we have a Tasker that can handle it (I don't understand why I didn't think of trying it for 2 years).
Create a new Task
Then we create a profile that will respond to the need to turn off the screen:
Event -> Display -> Display Off
From now on, whenever the screen is turned off, the lock screen image changes to one of the folders we entered.