One command for an instant, secure URL to your localhost server through any NAT or firewall.
Since version 2 ngrok is no longer open source and, as such, can't be added to the official Ubuntu repositories. This snap packages ngrok version 2.2.4, an older version as well, but one that doesn't require an account yet.
Please check the official ngrok download page for the latest and greatest. This is not it. This is an unofficial snap, I have no affiliation with the ngrok project and not liable for the ngrok software in any way. Use at your own discretion. The snap itself is MIT licensed, the ngrok binary is proprietary software.
Download the most recent version from https://ngrok.com.