Is an SD card a fair coin... to me?

I would say that the SD card itself is not a 'fair coin', since a reasonable requirement of a 'fair coin' would be that the probability of landing on each side is essentially 0.5 each.

However, I think the entire process as a whole of assigning an outcome to each side of the card and then flipping the card is a 'fair coin':

The reason why we need coins to make trivial decisions for us is that we can't just cycle through the 2 options in our head, stop at a random point, and choose the option we were thinking of at that point. Not only is this hard to pull off, but you can't be sure that you didn't subconsciously/consciously want to stop on a particular option.

Since the card decides the final result and we don't know the bias of the card beforehand, there is no way that your conscious/subconscious desires would have any way of manifesting themselves when you label each side of the card, and so you label each side essentially randomly, resulting in a 50/50 probability of your two options.