On southeast coast there are a couple of riding spots on the coast
Tathra, you can ride from the beach to the trails, flow mountain biking have a nice little video on this place.
Mogo Forest, specifically maulbrooks MTB trails near Browlee, though this is a little neglected as logging is planed at some point but the snake track is 2km of awesomeness
Or, head in land a bit to ACT and ride Majura, Stromlo and Kowen/Sparrowhill.
If in Victoria, I’d definitely go ride the Epic trail.