No matching method error after using range

Your RHS is not a matrix, but a Vector of Matrices, see this example:

julia> rhs = range( start=[1.0 1.0],stop=[2.0 2.0],length=2)
2-element LinRange{Matrix{Float64}, Int64}:
 [1.0 1.0],[2.0 2.0]

julia> collect(rhs)
2-element Vector{Matrix{Float64}}:
 [1.0 1.0]
 [2.0 2.0]

Each element of this vector/list is a:

julia> collect(rhs)[1]
1×2 Matrix{Float64}:
 1.0  1.0

With that, the +operator is not well defined, even .+ will not work I guess.

The range you are constructing, do you want this to be a row by row range, like in

julia> [1.0 1.0; 2.0 2.0]
2×2 Matrix{Float64}:
 1.0  1.0
 2.0  2.0

or do you want this to be a column to column range like in:

julia> [1.0 2.0; 1.0 2.0]
2×2 Matrix{Float64}:
 1.0  2.0
 1.0  2.0

From my example above:

julia> rhs = range( start=[1.0 1.0],stop=[2.0 2.0],length=2)
2-element LinRange{Matrix{Float64}, Int64}:
 [1.0 1.0],[2.0 2.0]

you can create the column to column matrix with:

julia> reshape(collect(Iterators.flatten(rhs)),(2,2))
2×2 Matrix{Float64}:
 1.0  2.0
 1.0  2.0

To make it a row to row matrix, you can use:

julia> collect(reshape(collect(Iterators.flatten(rhs)),(2,2))')
2×2 Matrix{Float64}:
 1.0  1.0
 2.0  2.0

Both transformations are perhaps not best practice, but for now I can’t find something shorter.