Thanks davidfor
I transferred the img file directly to my Kobo's internal micro SD card using the following method, and everything worked like a charm. The tutorial in the link below outlines how to swap your device's internal storage for a higher capacity replacement, but the steps are virtually the same if you want to flash an image to your existing card. Simply disregard the backup procedure.
The whole process took about 10-15 minutes and was very straightforward, but I would only recommend it as a last resort given the inherent risk of damaging your device's internals during disassembly.
https://www.mobileread.com/forums/sho...d.php?t=209122