Annoyingly, SubscriberStar demands your credit card details, something that I'm not comfortable handing over without an intermediary.
...........damn it all, I'll make a larger one-time donation through itch and paypal, and try to remember to make another one at some point. At least as much as I'd pay to get the game in a store. Hopefully at some point, an option for monthly payments will emerge that will be friendier to paranoid scaredy-cats like me.
EDIT: The current exchange rate between my country and the USA was not kind to my wallet :(