Please help! How would you fix this hole?

[Debedwardian]

Just removed the wallpaper in my new home and found this hole underneath, exposing some wood. How should I fill the hole before painting? I’m a complete beginner so would appreciate knowing which filler to use etc. Thank you!

 

[Sammy T]

I'd look for another forum mate. Very little help and interaction on this site.

 

[AC Power]

This is horse-hair lathe and plaster.

As this is no longer available, I would get some parging mix. This is a cementous based material, and has no large aggregate. Spray the existing horse-hair plaster with some water lightly, then apply the parge mix, trowel smooth, and sand it with a course grit sandpaper until satisfactory.