I don’t think there is a direct command for that, but you can use the Rails console.
First, you enter into it:
cd /var/discourse
./launcher enter app
rail c
Then, you find the user by its username (replace username_to_activate) and activate it.
User.find_by(username: "username_to_activate").activate
You can type exit two times to quit.
You should see that action in the log:
