Interesting. How did you do it, which SD type/vendor do you use and how did you format it (which OS, which tool?) My Sandisk SD is still not working as I would expect it some apps don’t see it of errors occur when they write to it. I also would like to reformat. (same reason btw. - big Signal backups but due to the fact that the FP4 has much more space not that urgent anymore as for the FP2. I also comment on this git issue for supporting chunked backups for Signal → introduce chunked backups by Roghetti · Pull Request #11900 · signalapp/Signal-Android · GitHub )
Open Camera: Maybe start reading this Thread 
: Camera & Camera2 API - missing features & bugs