This plugin provides an official integration with rex digital shop:
https://shop.rexdigital.group/

What does the plugin do?
The plugin allows you to sell forum usergroups as a product automatically.
The customer picks their desired product and duration and they receive it within seconds after buying.
Once their time is up we automatically downgrade them.
The plugins supports a user buying multiple products and will extend their subscription accordingly.

What is Rex Digital Shop?
Rex Digital Shop is an e commerce platform that helps merchants sell products to their customers.
We've partnered with Stripe to provide a bunch of payment options,
Many features is provided out of the box:
- GDPR Ready
- Customer Authentication with the '3D Secure 2' specification.
- PCI Compliance
- Advanced Fraud Detection

We also allow you setup:
- Staff Members - To have more people able to manage your shop
- Customization - So the store conforms to your branding / logos.
- Conversion Optimizations (Follow ups),
- Discount & Promotions

Payment Methods:
- Visa
- Mastercard
- American Express
- PayPal
- WeChat Pay
- Apple Pay
- Alipay
- Google Pay
- Microsoft Pay
- Bitcoin
- Ethereum
- Litecoin
- Monero
- Counter-Strike: Global Offensive Skins
- SOFORT
- iDEAL
- Multibanco

You can also create individual products which awards different usergroups (I show you how in the video below).

Thanks to mybb the installation process is very simple:
You can follow this video to see how:
[Video: https://www.youtube.com/watch?v=OzDC_Nkdwm4]