Unfortunately, AdPlexity doesn't have a filter that would sort ads by verticals at the moment.
​
You can use the search option 'By keyword', and you will find landing pages that include that keyword. So if you are looking for casino ads/landing pages, for example, you can try searching by keywords related to that vertical, such as: 'bet', 'casino', 'slots', 'bonus'...
​
Or you can use the search option 'By advertiser' and use your competitor (or someone you know is running that kind of ads that you are interested in) domain name/tracking link, to find all of their ads, if AdPlexity detected them.