At least on ubuntu 20.04, the python3 package is now 3.8, but the package 'python3' points to the current best version of python available without needing to specialize a minor version and should require fewer changes to the document.
@@ -12,7 +12,7 @@ Begin by installing all system packages required by NetBox and its dependencies.
### Ubuntu
```no-highlight
-sudo apt install -y python3.6 python3-pip python3-venv python3-dev build-essential libxml2-dev libxslt1-dev libffi-dev libpq-dev libssl-dev zlib1g-dev
+sudo apt install -y python3 python3-pip python3-venv python3-dev build-essential libxml2-dev libxslt1-dev libffi-dev libpq-dev libssl-dev zlib1g-dev
```
### CentOS
Aaron