15 sec adb installed the driver for the phone onto my computer which made this installer recognize it automatically, and then the installer moved past this stage. It's taking a long time to download and for the past few minutes hasn't moved past "Downloading file 1 of 12". I'll try these troubleshooting things, but I only have one cable.

I don't know how to return to the stock android recovery mode from UBports, but from this mode to Android actions I had cleared cache partition and data/factory reset. (I'm not tech savvy). I haven't gotten a different result.

No, I hadn't.

It is already on the UBports recovery mode screen during this error.

I am running this installer from Windows 10.