South March highlands isn't too far from you and has pretty good fatbiking on ungroomed trails. You can find it on the Trailforks app. Or just google it.
Gatineau park has groomed fatbike trails that you have to pay to use.
I hear the Larose forest has decent groomed trails but I haven't been there yet. It's east of Ottawa. You pay for the use by being a member of OMBA (Ottawa Mountain Bike Association)
The Almonte Riverside Trail is less than 30 minutes from you. A portion of that ("Bennies Corners") is groomed for fatbike.
Some NCC Greenbelt trails in the west end are ungroomed but fatbikable when conditions are right.
The Sir John A MacDonald Winter Trail is groomed for multi-use. That runs from Westboro Beach to the War Museum. It's flat and open and not super-exciting to ride, but scenic. There is a similar groomed winter trail in Orleans, east of downtown.
For more info, check out the Ottawa Mountain Bike Association (OMBA) on Facebook, or their website: