Like MyFitnessPal or something like that
To my knowledge no the most that I found where people on twitter documenting their wweight gain journey and i read that some of them have discords where you can get more information. But you may be able to find more information if you go to different social media sites that alow pornography since theey tend to satay ther so, twitter maybe tumblr, and reddit. Actually there may be some weight gain subreddit but it will most likely be disguised since weight gain is kinda considered by the social media sites as something harmfull to yourself.
Sorry I tried and see if I could get a link or something but well… Only health nuts kinda things appeared you know muscle growth and such so there is not much I can help sorry matey
there is r/weightgain, but again, it mostly consists of people posting pics of them gaining, but maybe there’re some posts that contain info, i didn’t really look far into the sub.