Discord is a wildly popular messaging platform among gamers, offering plenty of tools for organizing a gaming session or livestreaming. Some of the more advanced features like large file uploads and higher stream resolution require a subscription, and as of today, those can be managed through Google Play, along with any other in-app purchases.
In the past, purchases made in the Discord app would be handled by the company itself, rather than Google's own IAP processor. Google recently started cracking down on apps that circumvent its system, so Discord making this change may stem from that. Regardless of the reason, this is a great change for users. I recently got a new card, and having to go through each of my subscriptions to update my info is a pain in the neck. Having as many services routed through Google Play as possible means I'll only need to update that info once.
There are a few kinks for those of us who already have a subscription, though. According to the FAQ, if you wish to keep things as they are and pay Discord directly, you'll only be able to manage your plan on the desktop app/website. The Android app will be Google Play only. If you want to move your existing plan over to the Play Store, then you'll need to cancel it and renew once it's fully lapsed. To make things even more complicated, canceling your existing sub and then renewing through the desktop will make you lose your streak, but signing back up through Google will let you keep it. It's a bit convoluted, so I suggest you read through the main announcement post before changing anything.
This move is rolling out now and is already live for me in the UK, and hopefully it should be live for you too, soon.