1. Native and downloadable podcast apps! Most have browse/discover features, and a search field to find the topic you are looking for.
2. Listen Notes. A dedicated podcast search engine designed to find you both podcasts dedicated to the topic you're interested in, or episodes of ANY podcast that might talk about what you're looking for. You can filter by publication date and language too.
3. Standard search engines. Try a regular search engine with keywords and the addition of "podcast" to find what you're looking for.
Want to make a Podcast? Check out these links/resources for ideas on getting started:
Podcasting 101 from the Bello Collective- https://bellocollective.com/podcasting101/home
The Bello Collective is an excellent authority on podcasting. This page links to lots of articles and posts that they have published on the basics of podcasting from soup to nuts.
Tools & Equipment- https://www.podcastinsights.com/podcast-equipment/
You can do a podcast pretty inexpensively, but to do it well still requires some equipment and software. Equipment and software are changing and improving all the time. Here's a 2019 list of the basics and suggestions for getting started.
Preserving your podcast, tools from Metro NY - http://preservethispodcast.org/
The jury is still out on what the long term preservation of digital media for future generations will look like. The Metro New York Library Council is hosting a series of workshops on how to create and store podcasts so they have a chance at longevity. They have also created an instructional Zine on the topic.