Try to remember if you have installed an application these last weeks. Maybe this cause the problem. Also if you're using Good Lock's lock star apk check your lock screen wallpaper setup or uninstall it.
It turns out that I had used an ADB command to push the gesture hints bar off the screen (Galaxy S20+).
./adb shell wm overscan 0,0,0,-42
It's the easiest, best trick ever, because it gives you the full screen but also doesn't have the negative effect of using the option to hide it in the actual settings which causes you to need to swipe in an arch to change apps instead of just swiping left and right. I had to revert it by using the same command but changing the -42 back to a 0.