Ubuntu opens to black screen with blinking underscore after installing 18.04

Hi, I'm a near-complete Linux newbie. I installed Linux on an old laptop for practice, and then took the leap to do it to my "real" laptop, but it is not working.

Steps to reproduce:

1. ThinkPad Yoga 12
2. Swapped out SDD with Windows for new SDD
3. Booted from USB with 18.04
4. Chose to install Ubuntu on new SDD
5. After installation, boots into blinking cursor

Steps taken so far:

1. ensured boot order was correct
2. attempted to go into GRUB menu, but can't
3. attempted to open terminal, but CTL ALT F1-6 does not work
4. made sure laptop was setup according to this guide (https://download.lenovo.com/pccbbs/m...paper_v1.0.pdf)
5. note this USB was used to successfully install 18.04 on another Lenova Yoga (non-Thinkpad)

Any assistance would be much appreciated. Note that I still can boot into the USB.

Other info:
While booted from the USB, I can see the volumes available:

Computer 3.9 GB / 4.0 GB available (I guess this is the USB?)
250 GB Volume /dev/sda1 (the new SDD, an intended boot volume which isn't working)
SSD-512 /dev/sdb2 (a preexisting SDD)

I've attached a screenshot from the intended boot drive.

https://drive.google.com/file/d/1hFY...ew?usp=sharing