I just renewed one of my wildcards. You indeed need to use DNS and the TXT records need to change every time. You would need to use a script to set the TXT records for auto-renew.
Tutorial: Install NodeBB on DigitalOcean/Ubuntu 20.04
Interested in installing NodeBB? The good news is that NodeBB is free and open-source forum software, so anybody can install and set it up, even you! This tutorial will help you get started in no time flat.
This is an updated post, with commands and best-practices updated to work with Ubuntu 20.04. View the original post for Ubuntu 18.04 here.
Click here to see the full blog post