I managed to solve it, reinstalled from scratch.
Don't show datetime in chats dropdown
When I'm open chats (dropdown menu) next to the teaser-content there is a date and time (teaser-timestamp timeago pull-right) of this message, but the date instantly disappears and is not visible.
Thanks for reporting https://github.com/NodeBB/NodeBB/issues/8838
In chat list not showing messages preview
@togan I believe I removed the preview there awhile back, so this is intentional