How do I add NON iTunes store downloaded (3rd party) podcasts?

After my upgrade to Catalina I haven't had a single issue........ until today. I download most of my podcasts manually, that's just how I do things. Only get episodes from the Apple Store on rare occasions. I never had problems just adding my MP3s to the Podcast section of iTunes.

Until, of course, iTunes stopped being a thing in Catalina. I have a bunch of new podcasts I want to transfer to my iPhone, and now there is this roadblock.

(I will not be looking at "just use Apple Store like all normal people" as an acceptable answer, all other answers are very welcome)