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

Question

$ 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)

Answer 1

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.

Answer 2

Logged in as guest, works for me albeit terribly slowly (see timeout messages). Use the mount command to check it's mounted before trying anything else.

java@Tests-iMac ~ % open ftp://ftp.census.gov

java@Tests-iMac ~ % mount
/dev/disk2s5 on / (apfs, local, read-only, journaled)
devfs on /dev (devfs, local, nobrowse)
/dev/disk2s1 on /System/Volumes/Data (apfs, local, journaled, nobrowse)
/dev/disk2s4 on /private/var/vm (apfs, local, journaled, nobrowse)
map auto_home on /System/Volumes/Data/home (autofs, automounted, nobrowse)
/dev/disk3 on /Volumes/JProfiler (hfs, local, nodev, nosuid, read-only, noowners, quarantine, mounted by java)
ftp://ftp.census.gov on /Volumes/ftp.census.gov (nfs, nodev, nosuid, read-only, quarantine, mounted by java)

java@Tests-iMac ~ % cd /Volumes 
java@Tests-iMac /Volumes % ls
JProfiler   Macintosh HD    ftp.census.gov

java@Tests-iMac /Volumes % cd ftp.census.gov 
ls%                                                                             java@Tests-iMac ftp.census.gov % ls
nfs server ftp://ftp.census.gov: not responding
nfs server ftp://ftp.census.gov: is alive again
nfs server ftp://ftp.census.gov: not responding
nfs server ftp://ftp.census.gov: is alive again
nfs server ftp://ftp.census.gov: not responding
nfs server ftp://ftp.census.gov: is alive again
2020Census              econ1977
AOA                 econ1982
CTPP                    econ1987
EEO_2006_2010               econ1992
EEO_2014_2018               econ1997
EEO_Disability_2008-2010        econ2002
Econ2001_And_Earlier            econ2003
about                   econ2004
acs                 econ2005
acs2002                 econ2006
acs2003                 econ2007
acs2004                 econ2008
acs2005                 econ2009
acs2005_2007_3yr            econ2010
acs2005_2009_5yr            econ2011
acs2006                 econ2012
acs2006_2008_3yr            econ2013
acs2007_1yr             econ2014
acs2007_2009_3yr            econ2015
acs2007_3yr             econ2016
acs2008_1yr             econ2017
acs2008_3yr             exist
acs2009_1yr             favicon.ico
acs2009_3yr             foia
acs2009_5yr             geo
acs2010_1yr             govs
acs2010_3yr             hhes
acs2010_5yr             inc
acs2010_SPT_AIAN            incoming
acs2011_1yr             indicators
acs2011_3yr             library
acs2011_5yr             lost+found
acs2012_1yr             main
acs2012_3yr             media
acs2012_5yr             mount
acs2013_1yr             mtis
acs2013_3yr             mytouch
acs2013_5yr             news
acs_latest_data             not
acs_special_tabs            outgoing
adrm                    plmap
aff                 prod2
akamai-sureroute-test-object.htm    programs-surveys
cac                 pub
census_1940             qwertyuiop.test
census_1980             retail
census_1990             robots.txt
census_2000             sam
census_2010             services
ces                 software
data                    tms_data
decennial               topics
doe                 trade
does                    w3c
dssd                    wholesale
econ

java@Tests-iMac ftp.census.gov % pwd
/Volumes/ftp.census.gov