Under the banner of something or someone, there are several synonyms that can be used to convey the same meaning. One possible synonym is "in the name of," indicating that something is being done or said on behalf of a particular cause or person. Another possible synonym is "under the auspices of," suggesting that something is being organized or implemented with the support or sponsorship of a certain organization or individual. Other options include "with the backing of," "under the leadership of," or "as part of a movement or campaign." Regardless of the synonym used, the phrase "under the banner of something" typically suggests a unifying or rallying aspect to the situation at hand.