Creating a custom Network in ArcGIS Online for Route Solving

[LindsayRaabe_FPCWA]

Is it possible to publish a custom network to ArcGIS Online (not Enterprise) for the purposes of Network Analysis (route solving) with multiple travel modes, or are we restricted to ArcGIS Pro for custom networks?

[LindsayRaabe_FPCWA]

Surely someone here has some idea or can point me to a good guide/resource to digest? I haven't had much luck finding documentation on this myself.