DOUBT IT!!!! So, first off, this expert advice is assuming your training and recovery are both on point.
So are you a Hardgainer? I highly doubt it, most "hardgainers" just don't eat enough. It's a lot harder to put on size while on keto or only eating chicken breast, broccoli, and rice.
If you're skinny and trying to put on size get over it, be willing to lose your abs for a bit, and dirty up the damn diet. Don't be afraid to eat a cheeseburger or pizza every once in awhile. Track what you're eating. If you're actually being consistent with macros then you need to eat more.
Most guys that claim hardgainer status simply don't eat enough. True hardgainers are very few and far between. You know, Rich Piana was actually on to something when he kept preaching "eat more". Keep your same diet, but eat a damn cheeseburger or pizza. Eat more food.
Can I push the point anymore? Eat more food.