Install

# install reuired packages
apt install -y unzip python3-tornado

# download and instal script-server
mkdir script-server
cd script-server
wget https://github.com/bugy/script-server/releases/download/1.15.2/script-server.zip
unzip script-server.zip
rm script-server.zip

# start script-server
./launcher.py

Add job

# cat ./conf/runners/certgen.json 
{
  "name": "certgen",
  "description": "Request Lets Encrypt certificate",
  "script_path": "/usr/local/bin/certgen",
  "parameters": [
    {
      "name": "Domain",
      "default": "example.com"
    }
  ],
  "output_files": [
      "/home/local/certificates/*${Domain}*"
  ]
}

WebUI
http://SERVER_IP:5000/

Redirect port 5000 to 80

iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 5000

Links
https://github.com/bugy/script-server