Hi, see http://bugs.debian.org/1082775.

Installing python3-uno gives

Setting up python3-uno (4:24.8.1-2) ...
/usr/lib/libreoffice/program/officehelper.py:94: SyntaxWarning: invalid escape sequence '\P'
  """Bootstrap PyUNO Runtime.

probably thrown by 

#!/bin/sh
set -e

# Automatically added by dh_python3
if command -v py3compile >/dev/null 2>&1; then
        py3compile -p python3-uno:amd64 
fi
if command -v pypy3compile >/dev/null 2>&1; then
        pypy3compile -p python3-uno:amd64  || true
fi

# End automatically added section

# Automatically added by dh_python3
if command -v py3compile >/dev/null 2>&1; then
        py3compile -p python3-uno:amd64 /usr/lib/libreoffice/program -V 3.12
fi
if command -v pypy3compile >/dev/null 2>&1; then
        pypy3compile -p python3-uno:amd64 /usr/lib/libreoffice/program -V 3.12 || true
fi

# End automatically added section

which the Debian package helpers add automatically for public modules. "import uno" doesn't warn, but maybe when it gets actually used?

Anyways:

This is due to this comment in officehelper.py:

    """Bootstrap PyUNO Runtime.
    The soffice process is started opening a named pipe of random name,
    then the local context is used to access the pipe. This function
    directly returns the remote component context, from whereon you can
    get the ServiceManager by calling getServiceManager() on the
    returned object.
    Examples:
    i.  Start LO as a service, get its remote component context
        import officehelper
        ctx = officehelper.bootstrap()
        # your code goes here
    ii. Wait longer for LO to start, request context multiples times
      + Report processing in console
        import officehelper as oh
        ctx = oh.bootstrap(delays=(5,10,15,20),report=print)  # wait 5, 10, 15 and 20 sec.
        # your code goes here
    iii. Use a specific LibreOffice copy
        from officehelper import bootstrap
        ctx = bootstrap(soffice=r"USB:\PortableApps\libO-7.6\App\libreoffice\program\soffice.exe")
        # your code goes here
    """

which is line 94... (cf. https://git.libreoffice.org/core/+/refs/tags/libreoffice-24.8.2.1/pyuno/source/officehelper.py) and which was added in https://git.libreoffice.org/core/+/d8978a8c4ffabd6b36a691fd3e2df68563808234

The Problem is the Windows Path in iii. and the \P in \PortableApps.. Maybe that example should be converted into UNIX paths to avoid that \P which is interpreted as a escape sqeuence by python.