[city41]

Apple more than anyone is hostile to the web. I still have a recurring iCloud charge I tried to cancel today. But I literally can't as it's not doable on any Apple website. You must use an Apple device or iTunes, neither of which I have.

[microtherion]

Apple has instructions for canceling subscriptions from non-Apple devices: https://support.apple.com/en-us/HT202039

As a last resort (e.g. if all you have is an Arduino), they advise you to contact Apple support.

I'm pretty sure it would be unlawful to have no way to cancel other than with an Apple device.