Generally you only need to submit them to three platforms:

* Youtube Music (replacement for Google Podcasts) * Spotify * Apple

Every other podcast platform uses Apple APIs to get your podcast info, and it will be available on, for example Pocketcasts, as soon as it shows up on Apple Podcasts.

There might be a few other smaller players that you still have to specifically submit to, some of them have died off. The ones above will get you to the vast majority of listeners.

Excellent, thank you!

RSS of course. I don't care what platform you use just make sure there is an RSS feed.

Of course. Can it be the RSS feed for the podcast website if that is the only thing on the feed?

Podcast apps that only support audio containers should just ignore other kinds of containers in the RSS like the one blogs use for posts.