Insert the pointed end of a spudger under the 5G mmWave antenna on the side closest to the center of the phone.

Pry up with the spudger to detach the antenna.

It may take significant force to detach the antenna. If the antenna isn't moving, apply a few more drops of isopropyl alcohol and try again.

Remove the antenna.

During reassembly, remove the old adhesive from the bracket and frame, then apply new adhesive.