True, the selection of the wrong cinnamon for health benefits is widespread
Luckily enough, I found out about this about a decade ago when I started adding medicinal cinnamon to my daily half-avocado, along with turmeric and ginger (plus pepper). It’s readily available by searching for medicinal or Ceylon cinnamon on eBay, as you mentioned. Western research has been reasonably consistent in confirming what Asian’s have known for hundred’s of years — that medicinal cinnamon improves the health of people with diabetes (me) and has strong anti-oxidant benefits.