Many adblockers use the EasyList of blocked domains/files, but somewhat lesser known is the EasyPrivacy list which already blocks many of these helpdesk and chat widgets .
1 - https://easylist.to/easylist/easyprivacy.txt
I know how to do it in uBlock and Ghostery but that doesn't mean I want to or that it'll be 100% effective.
(for those interested: ##.c-message--custom_response)
It's available on the website https://hellogoodbye.app