According to the upstream
configure.ac, version 2.4.7 of
ppp should be supported — in fact that's the default version if no plugin directory is specified when configuring.
However, instead of compiling the extension yourself, the simplest solution is probably to use the binaries available in the corresponding PPA; just follow the instructions for Debian and Ubuntu, which should also work with Mint:
Debian/Ubuntu users can now use my personal PPA to download and install the
sstp-client project via launchpad.
You can import the gpg key using the following command:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 61FF9694161CE595
Put the following two lines into the following file:
deb http://ppa.launchpad.net/eivnaes/network-manager-sstp/ubuntu xenial main
deb-src http://ppa.launchpad.net/eivnaes/network-manager-sstp/ubuntu xenial main
Then use your
apt-get command to get both