If you upgraded to 1.7 probably apart to v1.6 you have a new v1.7 “general” Julia environment in ~/.julia/environments and a new set of “general” Manifest.toml and Project.toml files there. AFAIK, the best is to reproduce everything from the scratch. Also probably best would be to keep as little as possible in the “general” environment and for particular projects to use separate environments as was the case in my previous posts (actually there was a separate Julia and a separate Conda environment at the same time). You may also try to copy Manifest.toml, Project.toml and PythonCallDeps.toml files from v1.6 to v1.7 directory, however, as you were advised in your other recent thread by very knowledgeable persons, its not always ok to do it. [How do you like Julia 1.7?]
I think so. Again, this example was using the separate Julia environment as well as PythonCall and its separate Conda environment. You may try without PythonCall; with only separate Julia environment and the GMT.jl package. My guess is, after reading some posts in this thread, that GMT.jl would use Conda.jl which usually works also ok but AIUI is probably not as versatile at least in some use cases as PythonCall but probably less heavy wrt space occupied on a storage drive.
BTW, how do you like the GMT package? So far I have been using Gadfly and CairoMakie and was planning to do some geo plots there. I have been reading that Vega.jl / VegaLite.jl is ok for plotting maps and recently came by kepler.gl which works in VS Code and Jupyter and as I was informed by a person who is very knowledgeable about Pluto, should also work there.