Reviving this. So I was able to us MSMDownloadTools to drop it into OxygenOS 10 and then was able to install UT. Weirdly, it still said Bengal in fastboot but worked anyway!

@MrT10001 To be honest, I have no idea. I know it says Bengal in the fastboot menu and this Billie2 version of Ubuntu Touch says it is Bengal when I try to install it; that's why I was kind of confused.

I went to install this on my device and it turns out the the device name is Bengal instead of Billie2. I live in the US and ordered it directly from OnePlus so not sure why this is a different device name. Nonetheless, can Bengal have this installed somehow?