That specific feature isn't currently available, but you can still remove specific channels from appearing in your recommendations. Simply select “Don’t recommend channel” directly from the three-dot menu next to the channel name. More: https://yt.be/help/bhZv
If you find a video that isn’t related to the topic you selected on Home, you can let us know by tapping the three-dot menu, and then “Not Interested.” Appreciate it! Also, to improve your recommendations in general, check out this Help Center article: https://yt.be/help/cJiM