MDF instead of Plasterboard?

[u/MajorGrumble]

Started stripping lining paper which was painted over in the spare bedroom and was all OK until I got to 2 narrow strips near the door. Firstly, am I correct that someone used MDF instead of plasterboard.

Secondly, what’s the best solution moving forward. I guess ripping it out, plasterboard and skimming, but can the MDF be treated with something, smoothed out some way and painted over so it looks OK?

[u/Brocklette]

That looks like sound board or fibreboard, i wouldn't start ripping that down unless you know what you're doing. It'll be there for a reason.

Personally, I'd dryline (plasterboard) over it