Yes, you can find it anytime. It seem that https://ninjactic.space/ has the data you need to know the number of active users posting on a particular board for a certain time span be it every minute, hour, day, week and month. I saw a max limit of just 2000 users stored in the database if you want to know how many active users are posting on the board you want. For a bitcoin discussion board, so far it has a number of active users between 1300-2000+ every month throughout 2021. However, because the site has limitation, I don't think we can find accurate data if the time span you use exceed 14 days or 1 month. Use a shorter timeframe if you want to get data on the number of active users on a particular board.