MineSweeper.cs

static int[][] Minesweeper(bool[][] matrix) => [.. matrix
    .Select((row, i) => row
        .Select((_, j) => matrix
            .Skip(i - 1)
            .Take(i == 0 ? 2 : 3)
            .SelectMany(r => r
                .Skip(j - 1)
                .Take(j == 0 ? 2 : 3))
            .Count(m => m) - (matrix[i][j] ? 1 : 0))
        .ToArray()
    )];