Same here on a FP5 running v3.1.4.
I’ve updated to this version 2 days ago in the evening (GMT+2). Yesterday I noticed increased battery drain. Instead of 1 day on a 80% battery till 20% it drained the battery to 40% in half a day. I’m not sure if it’s related.
20 minutes ago I started getting the same Advanced Privacy notification spam. I click the notification and closed the app. This does indeed not solve the problem. After some tries I managed to open the app information screen (I opened it from the recent app overview). From there I force closed the app. I openend it again and the notifications started. I did another force close and swiped the notifications away. After now starting the app everything seems normal now. Although in those 20 minutes I lost ~15% battery. I didn’t clear any cache or data. I hope this helps.
Edit: fixed typos