Probably would be best if you asked Spotify support if they let you add RSS feeds. I have a feeling their podcast support is kind of limited to what you can find in their app, you'd probably be better off with a dedicated podcast app like Pocket Casts, Overcast, etc.
The desktop app is not very well designed for podcasts either. I was trying to search for specific episodes of a podcast instead of scrolling through a list of 700 episodes and it wouldn't let me. It's honestly kinda shit.
Interestingly, the phone app does let me search for specific episodes. Whoever is managing the desktop app is not good at their job.
Unfortunately, it's not directly supported as an RSS feed. However, you can still enjoy the Bombcast on Spotify by searching for it within the app. Just type "Bombcast" in the search bar, and you should find their episodes available for streaming. Also, if you want to make your music, you can easily https://songlifty.com/spotify-promotion/ and be popular on this platform. I hope that helps!