Way to convert unity scene using C4D file with FBX?

I want to 'replace' a unity linked C4D scene file with an exported FBX of the same C4D scene because Unity's C4D plugin is no longer reliable. I can't find a way to do this. Any ideas?

PS this isn't like, one object such as a car model or something. It's an entire level built in C4D with fbx animation involved and lots of editing done already in Unity to the linked c4d file. (this is old, wouldn't build it this way now). The auto-import of the .c4d used to work great but sometime around the R18 update Unity stopped playing well with the c4d native files.

 

Hmm, so is this just not possible? My understanding is that Unity is converting the .C4D scene in Assets into FBX in the background. Is there no way to access that FBX that Unity generates and replace it with another FBX?

 

Have you tried this?

https://assetstore.unity.com/packages/essentials/fbx-exporter-101408