Problem migrating from 1.38.5 to 1.39.1 due to Composer dependencies

Hi Everyone,

We are trying to migrate from Mediawiki 1.38.5 to 1.39.1. The
webserver is Ubuntu 20.04.5 LTS, x86_64, fully patched.

At the step of installing Composer with its dependencies,[1] 'composer
install' is dying with the error message:

<BEGIN SNIP>
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for doctrine/dbal 3.4.2 -> satisfiable by
doctrine/dbal[3.4.2].
    - doctrine/dbal 3.4.2 requires composer-runtime-api ^2 -> no
matching package found.

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according
to your minimum-stability setting
   see <https://getcomposer.org/doc/04-schema.md#minimum-stability>
for more details.
 - It's a private package and you forgot to add a custom repository to find it
<END SNIP>

We are running the latest version of Composer:

   # apt-cache search composer | sort
   ...
   composer - dependency manager for PHP

And:

   # apt-cache show composer
   Package: composer
   Architecture: all
   Version: 1.10.1-1
   Priority: optional
   Section: universe/php
   Origin: Ubuntu
   ...

Please advise on how to proceed.

Thanks in advance,

Jeff

[1] https://github.com/weidai11/website/blob/master/mediawiki/wiki-upgrade.txt#L104