How to cd to a mounted ftp volumn on big sur?

$ open ftp://ftp.census.gov

I use the above command to mount an ftp server on Big Sur.

I can see it in Finder. But I don't have permission to see it in Terminal.

$ ls /Volumes/ftp.census.gov
ls: cannot open directory '/Volumes/ftp.census.gov': Operation not permitted

Does anybody know how to make it viewable in Terminal?

$ ls -ltrd ftp.census.gov
dr-xr-xr-x 1 theusername staff 512 2021/06/14-06:21:35 ftp.census.gov
$ mount | grep census
ftp://ftp.census.gov on /Volumes/ftp.census.gov (nfs, nodev, nosuid, read-only, quarantine, mounted by theusername)

This answer covers MacOS Big Sur as requested:

Your terminal app has probably no rights to access the volume. Please check System Preferences / Security & Privacy / Privacy.

In this screenshot you see my selection for iTerm (I use it instead of terminal). For Files and Folders I checked the Network Volumes option. This has to be enabled for the terminal app to reach /Volumes.

Most probably you denied this, when terminal asked you the first time. See this picture:

Enabling it should give you access to the network volume. If you never denied or accepted the initial choice, there are no options available. As an alternative you can also enable Full Disk Access for Terminal.