Yes you can connect your Apple Watch. To do this, you will need to connect your Strava account to FulGaz, and then your Apple Health account to Strava. This will then sync your FulGaz activities across to Apple Health.
Using your Apple Watch as a Bluetooth Heart Rate monitor:
FulGaz can't communicate directly with your Apple watch, but you may be able to link it via a third-party app. You will need an iPhone to run the app and a separate device for FulGaz (iPad, Apple TV, laptop, etc).
Install HeartCast on your iPhone -> https://www.heartcast.app
Pair your Apple Watch with HeartCast.
This transmits heart rate from your Apple Watch via a Bluetooth channel from your iPhone.
Your Apple Watch HR should then appear as "HeartCast" under the Heart Rate option.