Update of biber missing

[Karl Berry]

    ftp://ftp.fu-berlin.de/tex/CTAN/systems/texlive/tlnet (verified)
    Available platforms:
    [...]
    (i) universal-darwin

If you look at the subdirectory
ftp://ftp.fu-berlin.de/tex/CTAN/systems/texlive/tlnet/archive/
(easier on your actual filesystem, if you have access to the machine,
which I'm guessing you might) and the files
  biber.*
there, you will see biber.universal-darwin and no biber.x86_64-darwin.

Do you have a bin/universal-darwin/ subdir in your TL installation?
I'm guessing yes. That's what the TL21 installer would have created.
I surmise your x86_64-darwin is left over from 2019.

Question in my mind is, do you just install each year over your previous
/usr/local/texlive? As opposed to moving the previous year aside before
doing the new install.

Installing in the same dir doesn't seem like it should work at all. You
would end up with many inconsistencies, as packages get renamed, not to
mention files getting moved around even when the package name stays the
same.

I can't recall offhand if we give any warnings when installing to an
existing directory ... --best, karl.