A couple of things I notice.
Firstly, the PATH that you quote includes (twice) the string
/home/clement/Julia_folder/julia-1.5.2/bin/julia
That is the file that you’re trying to execute, not the directory that contains it. No matter where that is in your path, the operating system won’t find the executable.
Secondly, the line you have in your .bashrc,
export PATH="/path/to/home/clement/Julia_folder/julia-1.5.2/bin:${PATH}"
has not been successfully imported into your shell. Perhaps you didn’t do source ~/.bashrc after your most recent edit.
Finally, your Julia LOADPATH won’t change until you are running the correct executable. What do you get if you run which julia? If that gives the correct result, are you running R from the same shell?