I really like my M6 MkII...but...I'm perplexed about the external flash situation. Its not a plug and play situation, at least not with the Yongnuo 560 IV flash I got. I loaded the batteries, mounted it to the hot shoe, went to make sure the camera flash settings were right...and got a message stating the flash was not compatible or the power was turned off...I'm a modern camera noob so forgive me if I'm missing something simple. The flash power was on so that leaves only one other possibility. If in fact that is the case, that the flash is not compatible, which flash is compatible. There seem to be a lot better offerings from after market copanies than Canon's Speedlight flashes. I could not find and answer to my question by searching this forum so forgive me if it is already posted.
Price. After market flashes are more affordable and I would suspect as reliable.
Do some research. The Yongnuo speedlights are not fully compatible with anyone's gear. Buy a Canon model.