Tex Live and tlmgr.

[Karl Berry]

Hi Rolf,

    > (running on Debian, switching to user mode!)

Evidently you're using the TL that comes with Debian (/usr/share/texlive
..). This is entirely separate from the "upstream" TL distributed by
the user groups (https://tug.org/texlive).

I know nothing about updating the Debian package, but presumably you
already have the latest TL stuff that's available for whatever Debian
version you are running, because Norbert is quite active :) about
keeping Debian as up to date as possible.

    Or something else entirely???

You can install the upstream TL, either from the .iso as Alan suggested
or starting from a small installer, as described on
https://tug.org/texlive/acquire-netinstall.html

    whole Tex Live installation will go to hell in a handcart and I will
    lose, for the time being, the capacity to use LaTeX.  I cannot afford
    that.

By default, the upstream TL will install under /usr/local/texlive and is
*entirely independent* of your distro installation.  Many of us have
myriad TL installations and switch between them merely by changing PATH.
You have to go to some trouble changing default directories and/or
options to create any interference ... --hope this helps, karl.