What's the best option for a self service Teams request process (Bot, Adaptive Card, App)?

Thomas_Steibl you may find this useful.

Updated:

You can avoid group and Teams duplicate names by implementing a self-service request for Teams. 

This solution also gives Admins more control over naming convention and blocked words. You can modify the script to your preferred naming conversion. Or simply use it as is. You would need a PowerApps form to capture the requests, a SharePoint site to store the requests and an internal email relay server to send request status to users (or use PowerAutomate send email feature). All that is described in this article.

https://insterswap.wordpress.com/2020/03/25/how-to-develop-microsoft-teams-self-service-app-to-fix-the-duplicate-display-name-limitation-in-the-teams-client/

Lastly, you would need to create a scheduled job for the script and let it run every 5 to 10 mins interval to process user requests in the background. Mine runs every 5 mins. Good luck!