every ones in a while there is a pop up on the main page which asks to join the Frontline pioneers ones you accepted it's important to join a frontline pioneer map (use the advanced game filters) else you'll be kicked out due to inactivity
There is a limited amout of slots for frontline pioneers so in case all are currently filled, the pop-up will only show up after someone left the pioneers. There is always some fluctuation so you should get the chance to join eventually.
Seems I get a pop-up for Frontline Pioneers daily as I log in, possibly because I spent a year playing such maps.
You can rest assured that we are all BETA TESTORS for S1914, there is no benefit to playing Frontline Pionieer maps from my perspective, if Bytro Offered some compensation perhaps I would again be interested in joining such maps.