Domains
Use a domain name instead of an IP address.
You usually don't need to set up the domain on the VPS. Point it to the VPS IP in your DNS provider.
Players then join play.example.com. If the server uses a port other than the game default, add it: play.example.com:25566.
Cloudflare
Turn the proxy off (grey cloud). Cloudflare's proxy only carries web traffic, not game traffic.