Question Apple GameCenter Alternative

I’ve been working on a game for a while now, which is a 2D multiplayer Async game.

At present it is iPhone / iPad only as the match making and turn handling is all built over Apple GameCenter.

I’m wondering if anyone has suggestions for alternatives that work with Unity.

I’ve looked at a few like BrainCloud, but the issue I have with a lot of them is they expect both players to be online at the same time to start the game, where as GameCenter will allow you to start a game against “nobody”, make your move and submit it and when one one else starts a new game it’ll pair you up. Alternatively if you start a new game and someone else is waiting already it’ll pair you up and load their move on to your device for you to take your turn.

I want a service that works the same way as the GameCenter match making for turn based but is cross platform.

Any suggestions would be a big help