Big Sur: PDF Service shell script cannot call python

I recently upgraded from Mohave to Big Sur, and the shell script I use as a PDF Service has stopped working. The script calls a Python script to process the PDF, and this gives the error "operation not permitted". Thinking that this has to do with the new security restrictions, I tried dragging everything that seemed relevant to Full Disk Access in the Privacy pane of the Security & Privacy settings, but that didn't help. Here is the script with some debugging lines inserted:

#!/bin/sh

export PATH=/Library/TeX/texbin:/usr/local/bin:$PATH

########################################
# Log stdout and stderr (from https://stackoverflow.com/a/20564208).
LOG_FILE=/tmp/pdfbooklog.txt
# Close STDOUT file descriptor
exec 1<&-
# Close STDERR FD
exec 2<&-
# Open STDOUT as $LOG_FILE file for read and write.
exec 1<>$LOG_FILE
# Redirect STDERR to STDOUT
exec 2>&1

########################################
# Get name of file printed and print options (unused).

# name or title of file printed, e.g., document.odt
TITLE="${1:-}"
# space separated options from the print dialog: k1=v1 k2='v2' …
PRINT_OPTIONS="$2"
# Make first (usually only) filename $1.
shift
shift

# Some programs called write files to the current directory, so make sure
# we're somewhere where that will work.
cd /tmp

########################################
# Apparently it's possible to be called with multiple filenames.
# Use a loop to make sure we handle all files listed on the command line.

for f in "$@"
do
    echo "Processing '$f'"
    echo "PATH: $PATH"
    /usr/local/bin/python3 -c 'print("Python works")'
    pdfbook2 --inner-margin=80 "$f"
    open "${f%.pdf}-book.pdf"
done

When I invoke it from the print dialog, this is what is written to the log file:

Processing '/var/folders/2j/w5jh3df55p7f4n05nh_m45jr0000gn/T/printing.11142.10/test.odt.pdf'
PATH: /Library/TeX/texbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
/Users/me/Library/PDF Services/Make PDF booklet.sh: line 40: /usr/local/bin/python3: Operation not permitted
/Users/me/Library/PDF Services/Make PDF booklet.sh: /Library/TeX/texbin/pdfbook2: /usr/bin/env: bad interpreter: Operation not permitted
The file /var/folders/2j/w5jh3df55p7f4n05nh_m45jr0000gn/T/printing.11142.10/test.odt-book.pdf does not exist.
test.odt-book.pdf does not exist.
Done

pdfbook2 is included with MacTeX: it is a Python script that invokes python3 with /usr/bin/env. python3 is in /usr/local/bin (installed with Homebrew), and as the test line shows, I cannot even invoke it directly. What do I have to do to permit Big Sur to run this script?

Update:

• In case it wasn't clear, the script works when invoked from the Terminal. It only fails when it is invoked from the print dialog.
• Since Big Sur still has /usr/bin/python3, the script above can be modified to use it. When the PDF Service is invoked from the print dialog, /usr/bin/python3 -c 'print("Python works")' will print "Python works". /usr/bin/python3 /Library/TeX/texbin/pdfbook2 --inner-margin=80 "$f" will begin executing, but pdfbook2 will then throw a PermissionError of "Operation not permitted" when it tries to run pdfcrop, which is also in /Library/TeX/texbin.
• The first line of pdfbook2 is #!/usr/bin/env python3. The first line of pdfcrop is #!/usr/bin/env perl, which should find /usr/bin/perl, since there is no Perl in my /usr/local/bin.
• So apparently SIP is preventing PDF Services from execing anything that is not in a protected directory, and from using /usr/bin/env as an interpreter (which could circumvent that restriction). Is there any way to give a script permission to do this? Giving the script Full Disk Access doesn't work.