Note: this was performed back in 2019.
# Create additional pulse audio config directory if not already exists
$ sudo mkdir /etc/pulse/default.pa.d
# Create additional config
$ sudo nano /etc/pulse/default.pa.d/reversed.pa
load-module module-remap-sink sink_name=reverse-stereo master=0 channels=2 master_channel_map=front-right,front-left channel_map=front-left,front-right
# Uncomment below if wanting to set as default
# set-default-sink reverse-stereo
# Restart pulse audio NOTE: run without sudo
$ systemctl --user restart pulseaudio
Now you should be able to view the new audio device in Sound settings.