If I use TigerVPN, my Slingbox works in MacOS El Capitan. It doesn't seem to matter which country I use it on (tested Canada, USA & Britain)
I also have a SurfEasy USB dongle but the version of SlingPlayer that I am using does not work with it.
I am using SlingPlayer 188.8.131.522 and a very old Slingbox SB240-100.
I'd love to upgrade to an M1 or M2 if anyone has one 4 sale, max. $50.00