HRM is kinda average for gravel riding but there are some loops that we’ve put together over the years. One is nicknamed the Bear Scare, it’s out in Tantallon: https://www.strava.com/activities/75625529#1507441540
You could cut off the yankeetown section and roll it to/from the Train Station Bike and Bean pretty easily for about 75k. Make sure you’re running tubeless rubber or lots of pressure if using tubes.
Other popular routes that you’re prob aware of are the rails-to-trails both on the COLT and on the Salt Marsh trail. No real elevation gain/loss but scenic and as easy or hard as you want.
Ideally if you can get to the Annapolis Valley, East Hants or Colchester you can find hundreds of kms of great terrain for gravel riding since they have more dirt roads.