Welcome, @KJW!
Depending on whether or not you have conda installed, you might need to specifically first create the .venv inside the galaxy directory with virtualenv. Install that first if you don’t have it.
The process goes something like this…
Make sure you are in the galaxy home directory:
$ pwd
/Users/me/1901/galaxy
Create the environment:
$ virtualenv -p /usr/bin/python .venv
Running virtualenv with interpreter /usr/bin/python
New python executable in /Users/me/1901/galaxy/.venv/bin/python
Installing setuptools, pip, wheel...
done.
Startup/initialize Galaxy:
$ sh run.sh
< a bunch of output logging ending with ... >
Starting server in PID NNNN.
serving on http://localhost:8080
Note: This was true last time I checked, and I still do it when starting up a local on MAC OSX. The admins can correct me if no longer needed and something else is going on!