Yet another sudoku app. And yet another sudoku app name that has been used before. I should make a game "Can you think of a catchy sudoku app name that has not already been used?".
To generate a random sudoku use https://qqwing.com/generate.html, select the output format "One line" and uncheck any of the options below that.
Some solving methods can be found at https://www.conceptispuzzles.com/index.aspx?uri=puzzle/sudoku/techniques.