Disclaimer: unpopular opinion from somebody who has always been in the same boat as the OP (naturally lean/slim, low appetite, general dissatisfaction from eating)
If your appetite is holding you back and you are lean + in good health you should really consider utilizing things like fast food/pizza. For example, you can get 15 boneless chicken wings from wing stop, buffalo wild wings, hooters, etc. and get roughly 100 grams of protein and 1.2k+ calories from just that meal alone. Throw a fries and soda alongside it and you’re easily at 1600+ calories in just that one meal. Whole pizza with meat toppings = 1500-2000+ calories, 100g+ protein. McDonald’s triple cheeseburger = 500+ calories 35? grams of protein in each burger. The list is endless. It may not be the most healthy, but neither are steroids, and if you are trying to put on size while using steroids but are unable to eat sufficient calories, you’re doing yourself harm for no gain since you can’t build muscle without adequate calories + protein. Throwing in a meal of fast food to replace one of your current ones could be a huge difference maker if you’re currently eating meals that are 1/2, 1/3 or 1/4 the calories of the fast food. Without fast food I would be far more miserable trying to get in my calories/protein. Obviously this can’t be carried into prep or something, but if you’re bulking and in good health, IMO you’re only doing yourself a disservice by not giving “dirty” food a try.