As this is one of the first results on Google when searching for an Angular HTML WYSIWYG editor, I thought I would add to Elaine's comment about her settling on TinyMCE.
There is an Angular module for TinyMCE, ui-tinymce: https://github.com/angular-ui/ui-tinymce
Having just tried and failed to get Angular-Trix working, ui-tinymce appears to work quite well. Note that ui-tinymce appears only to work with TinyMCE version 4.3.12 or lower at the moment. The relevant issue is here: https://github.com/angular-ui/ui-tinymce/issues/264
Additionally, TinyMCE is also quite well documented: https://www.tinymce.com/docs/
Regarding your no jQuery requirement, the module does not explicitly list it as a dependency, so it may just be dependent on Angular's jqlite (or not at all).