Applications
Android App (Help Learn Basics (colours of squares and at higher levels they ask questions about from easy to very difficult)
Chess Vision App
Chessboard Vision App
Android Apps
Some of these apps show you a position for some preset time and then ask you questions about it. What White pieces does Black attack. How many undefended pieces does white have? What pieces attack and defend the white d4 pawn? I found these really hard with a lot of pieces and just a short time view of the board.
I order these by putting the ones that I have on both my phone and Android tablet first.
Visualization Trainer
Blindfold Chess (White icon with a Knight)
Blindfold Chess (green icon)
Blindfold Chess Offline
Chesvis (with openings)
Blindfold Chess Puzzles
Blindfold Chess Trainer
Blindfold Chess Training
Blindfold Chess Tactics
BC Tactics
https://chessmadra.com
https://www.chessvis.com
I tend not to like ads and if an app bothers me I would just uninstall it. So there could be good apps that stop the ads if you give them a small amount of money.