For anyone living in regions that are unable to find matches of Operations (Asia, Oceania), changing the region on your console will not work. You can either LFG, or find a friend in the US you can consistently join in on. If neither of those are options for you, the Clubs feature on Xbox One is your best friend.
Simply go to the game hub of Battlefield 1, press
twice to go to "Friends & clubs". You will see clubs related to Battlefield 1 here, and there's a well populated one called "Battlefield Veteran". Select it, and press
4 times to go to the "Roster" tab. This shows all the members in the club, and chances are some of them will be playing Operations on BF1. You can see this when it says "Battlefield 1 - MP: Grand Operations on [insert map here]".
When you find someone who's in this activity, select their gamertag and attempt to join in on their game. You won't be able to join on everyone due to some privacy settings that people have, so keep trying different people until the "Join Game" option is highlighted, meaning it can be selected. After that, it's just a matter of waiting for the game to load up. (There's a chance you may be in a queue to join the game, just give it some time.)
It may be an overcomplicated process just to play a match of Operations, but until DICE adds it into the server browser or fixes matchmaking for it, this is your best bet.