Interesting! Firstly, BuyMeACoffee does indeed take a cut. As for Ko-Fi, that they take 0% of subscription fees is the common answer to the Googled question 'does ko-fi take a cut of earnings '.
But in a related question 'how does ko-fi earn money', we get the following:

"Ko-fi earns money from donations to its own Ko-fi page, from Ko-fi Gold subscriptions, and from a 5% platform fee levied on commission and shop sales for creators that don't have a Ko-fi Gold subscription." - reviewgeek.com (September 9 2021)

I'm going to look deeper into this. But my current understanding is that Ko-Fi absolutely takes nothing from subscription/donation fees, but does take 5% specifically from non-Gold member shop sales.