This was improved in Julia 1.11. Now you can

1. ] add "https://gitlab.com/vyush/Xnumber.jl.git"

2. Add the URL under [sources] in Project.toml, like so:

   [deps]
   ...
   Xnumber = SOME-UUID # this should automatically be created by step 1
   ...
   
   [sources]
   Xnumber = {url = "https://github.com/JuliaLang/MyUnregisteredPackage.jl"}