  Laser pulses of extreme intensities ($I>10^{22}~ \mathrm{W/cm^2}$) are about
to become available in the laboratory. The prepulse of such a laser can induce
a plasma expansion that generates a low-density channel in near-critical gas
jets. We present a study of channel formation and subsequent direct laser
acceleration of electrons within the pre-formed channel. Radiation reaction
affects the acceleration in several ways. It first interferes with the motion
of the return current on the channel walls. In addition, it reduces the radial
expelling efficiency of the transverse ponderomotive force, leading to the
radiative trapping of particles near the channel axis. These particles then
interact with the peak laser intensity and can attain multi-GeV energies.
