Below is a brief guide on what to do if you want to connect Windows SSTP VPN from MacOS
Prerequisites: Homebrew installed - see here
Launch a terminal and install sstp-client
brew update
brew install sstp-client
To connect to your SSTP VPN using login and password, use the following command line:
sudo /usr/local/sbin/sstpc --log-stderr --cert-warn --user <user> --password <password> <server> usepeerdns require-mschap-v2 noauth noipdefault defaultroute refuse-eap noccp
If you prefer to use the interface to start a VPN connection, you can use iSstp
https://www.axot.org/2015/03/03/isstp-a-sstp-client-for-mac-osx/