A Cisco AnyConnect VPN alternative for Mac? Is it possible to use OpenConnect or some other VPN alternative on macOS? Has anyone done is successfully?

The only software I've been able to find saying it is possible is http://www.feingeist.io/shimo/ which costs €50 :-o
OpenConnect works great on El Capitan. I use the text commands to connect to my work VPN.

There's a Gist with a walkthrough of setup instructions using the Homebrew installer: https://gist.github.com/moklett/3170636

On El Capitan, the "rootless" protection prevents you from installing the unauthorized "tun tap" kernel driver extension that OpenConnect needs.

However, a Mac app called Viscosity comes with a signed (authorized) copy of tun tap. Viscosity has a limited trial, but the driver is free. https://www.sparklabs.com/viscosity/

Install Viscosity and run the app once to get the helper (driver) installed. Then use OpenConnect.