phenaproxima → credited donm → .
Thanks.
I did the manual edit of composer.json to version 10, as you suggested. I decided to run the 2nd item first:
composer update --lock -W
but it gave a "no change" message.
When I ran "composer install", I got a message to the effect that the .json file requirements conflicted with the .lock requirements:
This usually happens when composer files are incorrectly merged or the composer.json file is manually edited.
Read more about correctly resolving merge conflicts https://getcomposer.org/doc/articles/resolving-merge-conflicts.md
and prefer using the "require" command over editing the composer.json file directly https://getcomposer.org/doc/03-cli.md#require-r
Because composer re-generates the lock file when running 'update', I then ran
composer update -W
to see if lock would update, and that command worked to get Composer updating both Drupal and the needed dependencies. Will check this out on the other sites I need to update. Thanks, again.