I'm in the same predicament but slightly different parameters. My sources are Microsoft OneDrive directories buried in ~/Library/CloudStorage/ and my destination is a mounted disk image. My bash script runs fine in Terminal but I get the Operation not permitted errors when run from launchd. I'm running macOS 12.6 (Monterey) on an M1 based MacBook Pro.
I tried all of the following without success:
installed rsync 3.2.6 via homebrew and forced my script to use it via export PATH=/opt/homebrew/bin:$PATH
tried numerous variations of rsync options based off "-av" - e.g. rlptgoDv and deleted options one-by-one
created a test version of my script that used source and destination directories on my desktop rather than in my Library or on an external volume
Based on the number of postings I've seen on the Internet about this issue, I'm surprised there are no solutions!
Craig