This is a minor bug report. Since FAF is somehow parsing the list of enabled sim-mods for the host, perhaps you could add an exception to ignore 2x and other mods that everyone always has (like retirement, etc)
Or, technically, as I understand it, 2x is an actual mod, and gets it's own Lua file like any other sim mod. Perhaps someone could upload that Lua file to FAF so that it no longer shows up as "unknown sim mod"?