Update: had this information from the CiviCRM forums:
"In this specific case, my guess is that community builder is using guzzle 7 (the source code for community builder doesn't seem available online to check???). If that's true, then since civi supports guzzle 7 but just ships with guzzle 6, what you can try is go into the civicrm plugin folder and run
Code:
composer require guzzlehttp/guzzle:'^7'
so that they end up with the same version. If something goes wrong just
Code:
composer require guzzlehttp/guzzle:'^6.3'
to restore the old guzzle for civi."
Does this make sense? Can someone confirm the Guzzle version for CB, or have other insights?