What is the ruling on subscribing to a website that displays products and gives a commission for every purchase made through the product link, and another that displays visual advertisements and gives a commission based on the number of clicks or the value of sales?

If joining such platforms is free of charge, then there is no harm in it. It falls under the category of permissible brokerage, so long as it does not involve assisting in the sale of something forbidden, or guiding towards it. What the subscriber receives falls under the category of a commission (ju'l) for a permissible act.