For anyone else having this problem, I finally managed to solve it just by using a different computer. I followed the exact steps from this article: https://docs.onion.io/omega2-docs/Firmware-Flashing-Web-Recovery.html
Originally I was using my Mac to do the web recovery and was getting the error: Loading: ### Error: couldn't find start of data in next packet!
I switched to a different Mac and then the web recovery worked using the exact same steps and firmware binaries.