It's current version 2.1.4 has issue which prevents flashing of MyNode image to SDHC Cards on Windows at least.
Opening gives error
Something went wrong while opening mynode_raspi45_0-3-34.img.gz
Error: (0, h.requestMetadata) is not a function.
I got success with v1.18.11 Portable which can be found at:
https://github.com/balena-io/etcher/releases/tag/v1.18.11
Recommending old version is not nice, but new users sure will struggle when even flashing don't succeed. Some kind of change to instructions would be nice.
Maybe just ditch balena (cause of other conserns in its fuctions balena-io/etcher#4428 (comment)) and leave Raspi Imager?