I have been on a ketogenic diet for four years now, two of which were while I was in the navy and a 7-8 month deployment. its not massive gain, I don't think, but ive added 20 lbs to my lean body mass as measured by a SKULPT and Dual energy x-ray since the end of 2015 to now.
you absolutely can gain both mass and strength on keto.
id say that the benefits to being patient with the steady gain on keto would be:
You benefit more greatly from fasting
Fasting elevates growth hormone which is a precursor to IGF-1
Insulin sensitivity is improved so the ratio of IGF-1 to insulin will be higher as growth hormone is elevated.
there is more I could get into, but that's the gist. this means that what matters is your training regimen, not carbs.
I will say that being in a ketogenic diet is not 100% devoid of carbs. I still eat skippy peanut butter, brazil nuts and broccoli. just stay under 10g carbs and 40g protein per sitting, then the rest is high variety of fats.
This article suggests that there is not effect on performance.