u/HeinsGuenter

Based on the Fitbit Help Center page, the following features will be removed or discontinued during the transition to the new Google Health app:

Health and wellness

• Skin temperature minute-by-minute data: In the Google Health app, you’ll only see your daily and weekly trends.
• Estimated Oxygen Variation (EOV): EOV data is no longer available. You can continue to view your overnight blood oxygen saturation (SpO2) data in the Health tab.
• Blood glucose features: You will no longer be able to add symptoms or set check reminders.
• Food Plans: Setting specific calorie targets via "Food Plans" is no longer supported.
• Recipes: This feature is being removed for Fitbit Premium users.
• Snore Detection: This will no longer be supported for Fitbit Sense and Versa 3 users.

Fitness

• Day-by-day plans: For users in Public Preview, previous day-by-day plans will be removed.

Social

• Groups and Community Feed: These features are being removed.
• Direct Messaging: Sending and receiving direct messages and notifications from other users will no longer be supported.
• Usernames and profile photos: Unique Fitbit usernames and custom profile photos are replaced by your Google Account details.
• Social privacy settings: Sharing of and privacy settings for sex, height, weight, location, or friend lists will no longer be supported
• Badges: Existing badges will be deleted, and new badges will no longer be generated. If you have Google Health Coach, your coach will help to celebrate your progress and accomplishment.

Sleep

• Sleep Profile: Sleep Profile will no longer be available, and you will not receive monthly sleep animals.

Third-party connections

• Lifescan devices: Connections to Lifescan devices will no longer be supported.

I am especially sad about the oxygen variation and badges, so I hope getting more awareness of which features are removed will make Google more likely of integrating them again in the future.