

You don’t want to hang wallpaper on a textured wall. The bumps will show through and look bad. Plus they impede good adhesion.
I’m pretty darned good at smoothing textured walls, through the skim-floating or skim-coating procedure. You can do a Search here to read more.
Note: The slight texture in the second photos is from the roller that applied the primer. The photo is magnified many times. In real life, this wall is nice and smooth and ready for wallpaper.