How to completely remove a local package?

[heliosdrm]

dev and add do different things. See this answer in a recent thread (the original question was different, but may give you another perspective to understand what is happening):

Packages under /.julia/dev/ shared by different versions of Julia?

Are you actually intending to edit the code in the cloned version of the package? Or are you just trying to have two different versions of A as dependencies for two different versions of Julia? If the latter, don’t develop A; instead Pkg.add the version that you want to pin for the older Julia version. Note also that you can always download a new version of A to anywhere you want using any method you want. If you then develop(path/toA) you will use that version of A in that particular environm…

A more detailed explanation of the main pkg commands here:
https://julialang.github.io/Pkg.jl/v1/managing-packages/

For your particular case, if the dev’ed version of ’ MyPackagelives in.julia/dev`, maybe it’s still finding that it is there, and there might be a conflict due to the lowercase/camelcase names, but I’m not sure.

You can try to check if that’s what is happening: if the package is in .julia/dev, move it to another place (e.g. outside .julia), and try add again. Let’ see what happens.