The one way to be sure it is the starter motor is to confirm power to it. The idea that it is under the intake doesn't make things easy. LOL
There should be a white wire with a red tracer coming from the power distribution module under the hood. That is the trigger wire for the starter. That wire should get 12v when the key is in the start position. See if you can access that wire. The best place to test would be on the starter, but that requires the removal of the intake as you already know.
I attached the wiring schematic below of the starting system. You can use this as a reference. Also, here are two links you may find helpful:
If you haven't checked the starter relay and relay fuse, do that as well. If there is a different relay with the same part number, switch them. If there isn't, here is a link that explains how to test one:
Also, when you check the fuse, confirm it has power to and from it.
And one last thing. See if placing it in neutral makes a difference.
See pics below/pic 3 shows the starter relay location and fuse 53.
Images (Click to enlarge)
Friday, November 12th, 2021 AT 8:15 PM