Warning The package will no longer be detected starting from v1.42.0

[Richard (Rikki) Andrew Cattermole]

Unfortunately yes, this appears to be an unintended side effect of that PR.

The search paths in dub are all implemented together, one set of logic.

So add-path probably was never doing what was expected of it.

You will need to switch to add-local for each package, unless you want 
to work on dub :)