Catalina read-only filesystem issue

Thanks all. This worked for me

Summarizing.

Catalina ships with a man document for synthetic.conf - apparently Apple's intention on how to handle this situation (that their support folk aren't yet aware of). Thanks, VikingOSX!

I chose /System/Volumes/Data/data as the actual location; choose whatever directory you want)

Then, in a Terminal window:

sudo mkdir /System/Volumes/Data/data
sudo cp {location of data}/data /System/Volumes/Data/data (<--- not tested; I copied with Finder before thinking)
echo 'data\tSystem/Volumes/Data/data' | sudo tee -a /etc/synthetic.conf

Voila. /data on the read-only filesystem (kinda)

Thanks - that looks optimistic.