Can't delete NLA tracks/strips for linked objects

I linked a rigged model with several animations (actions). I were trying to delete some unused tracks/strips in NLA editor, but I don’t know how to do it.

I tried everything. Press X on the strip. Press X on the track. Delete from context menu. Delete the action from Outliner → Blender File. Nothing happens, and the tracks/strips are still in NLA editor.

It only happens when the the model is linked. I suppose that I need to make Library Override for the NLA? But I don’t know how. (The armature itself already has Library Override. I can freely pose it without problem.)

It seems to be a bug:

:anchor: T72629 Library Override: Support editing of animation data in overriden data-blocks. (