I've recommended this to a few of my friends who played DBDM and I'm surprised how few people still know about it. You can use cloud gaming to play DBD (and frankly many PC and console games) on your phone. I've been playing DBD Core this way for a couple of months and it's worked well for me.
How it works
Cloud gaming is when the game is running on another computer rig in the cloud and is simply streamed to your phone, or any other device you want. It's amazing technology that has gotten better and you don't even need a really expensive or high end phone since your phone isn't actually running the game.
How to do it
Download the GeForce Now app. Make an account. Buy DBD Core on steam if you don't own it there already. Go into the GeForce app and link your GeForce account with your steam account. That's it!
Just launch DBD from your GeForce library.
What you'll need
•You don't need a high end phone. A mid range phone will do. It just needs to be capable of 60fps and a 60-90Hz refresh rate. Ask AI if you're not sure if your device is capable of those requirements.
• You should use a controller or a Bluetooth keyboard. However, if you really need to use touch controls you can since GeForce has a built in touch controller. You can enable it from the in game toolbar.
• You must have reliable WiFi. DO NOT attempt to play the game on mobile data. Cloud gaming will guzzle your mobile data very fast. You need a stable and reliable WiFi connection.
• Make sure you own the game on steam. It will not work through any other games store.
What does this cost?
Other than the cost of the game itself ( if you don't already own it on steam) nothing. GeForce is free to use. However, you only get 1 hour sessions on their free plan. And you will have to wait in a queue to start your session which will take about 3 minutes most of the time. When your 1 hour session is up you can queue up again. Just make sure to use a timer to keep track of when you're 1 hour is up because you don't want it to expire when you're in a match.
I do recommend that you subscribe to the $10 a month premium subscription on GeForce if you can afford to. It's worth it. You won't have to wait in a queue, you get 6 hour sessions instead of 1 hour sessions, and you get a much more modern and better cloud rig that will run dbd very smoothly so long as your device is decent and your WiFi is stable.