Genocide is the word for this. The author who coined the term genocide considered the cultural erasure and othering of an ethnic group to be an integral part of the definition of genocide, and that these things by themselves were sufficient to label something as a genocide without needing mass murder in addition to these things.
The UN definition narrowed the scope of genocide because many member nations would refuse to sign a law that included cultural erasure, forced assimilation, and the like out of fear that they could be prosecuted under such a law. The idea that these things aren’t as serious and don’t count as “real” genocide is the result of the criminals getting to write the rulebook.
Here’s a great video on the topic:
