OP here, I actually managed to get this to work. I made this thread after talking with someone else who I know got it to work, but I was skeptical until I did it myself. I'd be a little more worried if they didn't just lay off their entire security team lol. Here's the order:
1. Connect your Discord account in the Patreon settings page.
2. Pledge to a creator with Discord benefits, the server should automatically appear in the server list of the account you connected and you'll receive the role.
3. Change your payment method for the pledge to something that's going to decline, expired card, prepaid gift card with like 3 cents, whatever you need to do to make sure the payment will FAIL.
4. Wait until the start of the next month/billing cycle.
5. About a day after the next billing cycle starts, you'll lose access to the creator's posts and get an email saying the payment failed, but you'll still have the role in the server.
6. Go to the edit pledge page and instead of fixing the payment method, just cancel your pledge outright.
7. If all went right the creator will disappear from your list of supported creators yet you'll still have the role on Discord.
8. At this point it's safe to disconnect your Discord account in the Patreon settings page, and you'll now have the role forever! (*Given that you stay in the server and the owner doesn't notice.)