Domains
Free subdomains for servers through Cloudflare, plus Cloudflare Turnstile for the sign-in page.
Stratum → Servers → Cloudflare. Stratum creates DNS records in your Cloudflare zone, so a server can be reached at name.yourdomain.com instead of an IP and port.
Set up
API token
In Cloudflare, create an API token with Zone → DNS → Edit for the domains you want to use, and paste it on the page.
Domains
Add the domains users may pick from.
Subdomains
Turn on subdomains. Pick a pattern for suggested names (default {identifier}), whether records are proxied, and who may claim or remove a domain: owners and subusers, or admins only.
If a server's allocation is 0.0.0.0 or a private IP, set Target IP to the public address the records should point to. For games that use a port, an SRV record is created as well where the game supports it (Minecraft Java does).
Users manage their domain on the server page Domain Manager.
Turnstile
Cloudflare Turnstile replaces the captcha on the sign-in and sign-up pages. Add the site key here and turn it on.
Suggestions
Use a separate domain for game servers, not the one your website and panel run on. A wrong record then never touches your main site.