You don’t have to have a Zwift account to do this or any sessions on the OD platform, just your phone / laptop like you have been doing / hopefully enjoying ?
You would need a Zwift Account to run the Custom Zwift file, and yes a smart trainer like a Kickr or similar would be of use there.
We developed this as an add on that we will deploy in training programs for events like 3 Peaks, or Around the Bay.