You should use an LTS (long term support) version of Unity. My suggestion would be Unity 2020.3.46f1, or the latest LTS version of Unity 2020. And also, older Unity versions usually don't have support for newer packages (or vice versa), so that's why I would suggest using a newer Unity version to develop your fangame. Because sometimes I find that some packages I use in my projects are only available for newer Unity versions. You can see what Unity versions I've been using for developing my projects in the screenshot below (look under the "Editor Version section).
And when you want to install a Unity version in the Unity Hub, just go to the "Installs" section, choose "Install Editor", and you can install an LTS version of Unity from there.
However, Unity 2020 LTS releases are no longer listed on the installs page, so you'll have to go to here and find the version you want to download. Hopefully this helps you out with deciding what Unity version you should use, and thanks for your game development related question!
