"Was comfortable in", "felt at ease in", "were accustomed to" and "familiar with" are some of the synonyms for "were at home in". This phrase is used to describe a situation in which a person or group of people feel comfortable and confident in a certain environment or situation. It can apply to physical spaces, such as a home or workplace, as well as to social situations or areas of expertise. Using different synonyms can help to vary your language and add depth to your writing, allowing you to more accurately convey the nuances of a given situation.