Since https://github.com/wikimedia/mediawiki-extensions-CommentStreams/commit/0152886f10654a23d8b08b3f5b2ed21cd461af80, CS does no longer support the current LTS of MediaWiki which is unfortunate.
Topic on Extension talk:CommentStreams
Sorry for the delay, and thank you for reporting this issue. Please test the patch at https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CommentStreams/+/567261. If it works and fixes the problem for you, please give it a +1. Thanks!