Problem crack between wood and brick

[dcoy]

Hello,
I have this long crack that runs around the perimeter of a pre-existing door that had been covered up before my time here.
It’s seems wooden panels (I assume ply) have been placed in the space and is quite hollow, and not entirely flat. I’m repainting this wall and would really like to fill and skim this wall, but aware that’s not going to work without installing plaster board.
Is there some solution to at least filling this crack and smoothing it (that will last a few years at least) between these 2 surfaces… without bricking up or replacing the wood panels?
Thanks for any suggestions

 

[^woody^]

Gouge the surface, bed some 100mm wide mesh in the plaster across the crack.

 

[dcoy]

I actually tried this, using mesh and skimming over it, with joint compound but it didn’t adhere to the wall particularly well.
Maybe I should try this again

 

[^woody^]

Not 50mm joint tape?

 

[dcoy]

sorry, I used 50mm Fiberglas mesh. Is this what you mean but 100mm?