For podcasts, here are the phases I remember:

• bring speakers into a shared, recorded dialogue.
• arrange and clip recordings to size, drop any bloopers.
• record the sign-on and sign-off segments.
• (no ads to be concerned for here).
• overlay recognizable leading and trailing music clips.
• publish to RSS syndication.

Keeping these in mind, here's a process I'd recommend:

• (you may already have a good process); Hook up a Mumble room, and record per-track so each source is clear.
• Bring recordings into Audacity and mix as needed.
• Ardour is able to do many special effects for a higher learning curve.
• Need any video for a change? You can also use OSS. PiTiVi, KdenLive
• You'll be sharing many audio files! I'm looking to hook up RustFS or MinIO to as independent and scalable online storage.
• Each producer can use RClone or SyncThing to push and pull copies of the media, much like DropBox.

You can adopt these pieces one by one, beginning with Audacity perhaps. I'd like to help by running the Mumble relay, and setting up file sharing beyond the (assumed) normal Google Drive. As a bonus, during my link-grab I came across a business that Audacity recommends - Audio.com seems like they can handle publishing and syndication.