Using comment view modes I can use the UI to create a new view mode for a comment type in Drupal 8, without problems, but I don't see how to use that view mode.

For example, I just want to have a teaser that shows only the first few lines of each comment, and not the comments on this comment.

How do I specify a particular view mode should be used for the comments on a particular content type?

Does this require Display Suite?
There isn't a way to do this without writing your own formatters. However, could you open a feature request in the core issue queue as this is a worthy configuration option for the existing formatter.