Keto is fine, but you need to CARB UP with a carb/protein drink right after EVERY TIME that you train. I had a lot of success with strenght gains/fat loss by drinking 2 met-rx or other MRP (80 grams pro, 40 grams carbs min fat) after each training session.
Nutrition is way overrated. With the keto make sure that you get 1 gram of protein for each pound you weigh and do carb ups and you should do fine.
Take a look at prisioners. They eat SHIT meals with TINY amounts of protein but they train hard and get VERY strong. The key to getting strong is and always will be
1. genetics- Some people will just get strong easily (we all know what I mean).
2. Training hard. If you bust your ass and train hard, with superior genetics then you will get strong.
3. Train smarter not harder sometimes. Switch exercises and keep up the variety.
I have really great genetics and I get stronger pretty easily so this is my opinion. I don't know what it's like for a hardgainer, but if you have the genetics and train hard, you can grow in keto!