On the patreon site, there is an option called update on the gts page above, click on it, there are 5 options, at different prices, you can buy from there and become a member of any of them, I guess after you become a member? There will be access to the game
once you become a patron depending on your tier you will get monthly updates, but you do not need to pay additional money for those, just the monthly fee and you'll have direct access to the latest versions. I recommend to buy once the lowest tier and try the system. It differs from other andif you like it you can upgrade your membership 👍