Short answer: Most Jains do not eat mushrooms.

Reason (brief): Jainism emphasizes ahimsa (non-violence) toward all living beings. Mushrooms are fungi that grow in a way that can involve harming microscopic life, and their harvesting is often considered to involve killing or disturbing small organisms. Because of this, many Jains avoid mushrooms as part of a strict vegetarian diet. There isn’t a strong, universal rule enforcing this in every community, but the common practice among both Digambara and Śvetāmbara Jains is to refrain from mushrooms.

If you’d like, I can explain how different Jain vows and dietary rules relate to other common foods (like root vegetables or fermented foods) in simple terms.