Install issue with T470 Thinkpad

I've been beating my head against the wall on this one, so hoping I could get some suggestions here.

I have a t470 Thinkpad with the following specs:

i5-6300u

Intel HD 520 Graphics

Broadcom wireless card

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I've used everything from rehabman's guide to using the EFI folders from "working" t470 configs, and every time I get a "prohibited" sign and have to restart the machine. BIOS settings all should be in order. Not sure what else to try here.