In the DC ON steady-state, the electric field exists outside the wires. Specifically the electric field exists "outside" the wire in the free space directly between the battery and the bulb. The "energy" comes from a charge flux through this electric field i.e. not electrons/charge carriers "flowing through the length of the wire". Indeed as you note, the electron drift velocity in a typical electrical wire is in the mm/s. No electrons are flowing all the way down the wire and back a light-second in distance.
The "energy" is conveyed via this "external" electric field. If we were to impose something to block this field, then the flow of energy would stop.
Yes, there is a magnetic field around the wire, but it's not moving. The electrons however are moving, albeit slowly.
So how is the energy being transfered in the non-moving magnetic field?
Is the magnetic field just a byproduct of the current beign conducted in the wire in the DC case?
We all know that magnetic fields can store and transfer energy, it's the basis for transformers and motors and inductors, all very basic theory. But it is how power (and hence energy) is transferred at DC? If so, how?
Yes, I'm postulating that the power/energy transfer via electromagnetic field theory is not valid at DC.
Let me try paint a more "complete" picture of the DC system with fields.
The battery can be thought of as an "electric dipole" where there is a positive side/terminal with slightly lower electron density and a negative side/terminal with slightly higher electron density and as a result there exists an electric field (and a voltage potential) between the positive and negative terminals within the battery as well as the surrounding space. [This imbalance is setup by the electrochemical reactions within the battery][This can also be though of conversely, the battery has a electric field which causes a charge imbalance] When the battery is connected to a load, charge carriers (typically anions) move against the electric field (against the potential) thus there is generation/sourcing of electrical energy/power.
When the load (let's just assume a simple resistive load for simplicity) is connected, the electrons being "pushed" in see a resistance and bunch up on one side while spreading out on the other. Again there is an imbalance of charge and an electric field (and voltage potential) develops across the load. For the load however, the charge moving "with" the electric field so there is loss/sinking of electrical energy/power. In the ideal case where the load and the source are connected with an ideal (lossless) wire, the electric dipoles of the source and the load will perfectly match, in other words the voltage across the source and load will be equal but opposite relative the direction of electrical current.
Now we ask "how is the energy being conveyed?" There is no electric field in the (ideal) wires, any flow of charge through the wires has no generation/loss of electrical energy by definition of the wires being ideal wires in a DC system. In fact, in our theoretical system, the perfectly matched source and load dipoles effectively (but not completely apart from within the wire) cancel each other out with only substantial fields in a parallel region between the dipoles. Again, where is the energy "coming and going"? the creation and loss of electrical energy (from and into other forms) happens only "inside" the source and load.
But what if we disconnected the wire? Without an exit for electrons to flow out of the source negative and without a supply of electrons to flow into the load negative, the flow will stop. The imbalance across the battery will remain but the continuous imbalance across the load resistance will actually disappear as electrons spread themselves out within the load resistor till there is zero electric field within the resistor. [The resistive load will actually being an opposite polarity dipole in order to cancel out the net electric field within is self, no net current flow so no energy]. Now we can see the purpose of the wire, it supplies/takes charge carriers from the source and load terminals in order to continue the ON state equilibrium: On the negative side wire, some electrons leave the battery negative and enter the wire and some other electrons exit the wire enter the load negative. On the positive side wire, some electrons leave the load and enter the wire while some other electrons leave the wire and enter the battery. You don't have electrons travelling the full length of the wire (mostly, statically). You have some jumping on, some jumping off. There is a net zero charge change in the ideal wire itself.
Thus we see the "true" purpose of the wire is just charge conduit to maintain an certain equilibrium where there is a flow of electrons through both the source and the load but no net change in the total charge of the system, charge is cycled in a circular manner between the source and load, a "circuit" if you will
The actual "energy" is coupled via the electric field.
Edit: Attached a rough sketch. Might be much prettier if someone can to do a complete 2D field sim instead... I wonder if FEMM can do it, otherwise maybe something in Python...