Of the options:
1. Quick, easy, but not free:
Uber/Lyft
2. Shortest walk of the free options, but the bus might not run that early:
Boardwalk to Hollywood via walkway, then bus to Poly
3. The scenic route, with bonus security checks:
Bus to MK, then boat or Monorail to Poly
4. Feeling crazy (park ticket required), but also impossible to do early in the morning:
Walk through Epcot to the Epcot monorail at the front, then head to Poly from TTC
Sadly, it’s not free but there’s a lot to be said for Option 1 compared to the others!
[Edit:] Wildcard:
Does the Swolphin bus go to TTC?