Fedora Linux Users: can use the script bin/install-linux-fedora-33 in conjunction with Python 3.8. There is no wxpython wheel for Python 3.9 so simply install Python 3.8 using pyenv e.g.
$ sudo dnf install make gcc zlib-devel bzip2 bzip2-devel readline-devel sqlite sqlite-devel openssl-devel tk-devel libffi-devel
$ curl https://pyenv.run | bash
Remember to update your .bashrc and restart your shell.
Now that pyenv is installed, install a version of Python
$ sudo dnf install python3-devel
$ PYTHON_CONFIGURE_OPTS="--enable-shared" pyenv install 3.8.8
Now that a specific version of Python is installed, activate it globally or just locally
$ cd pynsource
$ pyenv local 3.8.8
Run the script that installs Pynsource and its dependencies
$ bin/install-linux-fedora-33
Finally, run Pynsource
$ bin/run
Alternatively run the prebuilt Fedora Pynsource binary from the terminal like this
`./Pynsource`
and it should start up ok, even though it is of a type application/x-sharedlib. Unfortunately double clicking on the executable from file manager in Fedora doesn't seem to work.