Prepping painted wall before lining paper, what to do with partial layer of vinyl paint?

[PanickingAmateur]

Hi all

I'm preparing my living room wall for lining paper. There's a layer of rock solid vinyl paint directly over the plaster, which a previous occupant has partially removed in a circular fashion over about half of the wall, then painted a delightful 90s pink over.

I discovered this after removing 3 layers of wallpaper. I was going to prep the wall and thought the lining paper (Erfurt wallrock) would hide the discrepancy between the vinyl layer and bare wall, but now I'm questioning if it will? I've attached photo evidence and am now feeling horribly daunted that I may have to get a hammer and chisel out (joking but not far off!)

Any advice welcomed!

 

[88v8]

A bit late, dare say you have done summat by now... I would sand it with a detail sander, see if you can flat it to a taper edge.
Then try one drop of the lining paper and see.
If you are wallpapering over the lining paper, I would think you'd be OK.
Matt paint, perhaps OK.
Anything shiny, perhaps not.
Avoid putting wall lights where they would shine on any dodgy areas... nothing like oblique light to show up imperfections.