This is actually very sad because last year i bought the dlc and couldn't play on any of the maps. The real reason why this was not fixed is because you at the time of the DLCs release Battlefront 2 was nearing release and EA wanted to leave the BF1 players with as little content as possible so they would purchase the $80 Battlefront 2. I actually refunded the DLCs because I couldn't play any of the maps or modes but repurchased it later because the heroes it comes with is still worth that $20 to me.
1. If you want to play it badly enough there are communities of gamers who play BF1 and schedule times to play certain maps at.
2. Or if you have any friends who have the DLC you can create a private match in which you can play any map or mode as long as you have two players (no, this does not support splitscren, i've tried)
3.If you are on PC then you can use this mod: https://www.nexusmods.com/starwarsbattlefront2015/mods/424
I am also pretty sure this is every possible method since i have been in your situation too
