This guide explains how to install the VyOS Rolling Release (free nightly builds) on Hetzner Cloud VPS. This might also work for other VPS providers with the proper rescue system in place.
First log into Hetzner Cloud, switch to your VPS control panel, select Rescue -> Enable Rescue and Power Cycle. It takes up to 1 minute to boot into rescue mode. Your login details will be displayed in the control panel after you activate the console. You can also use previously defined SSH keys.
Download and write the ISO image in the Rescue environment: