Unity Hub does not give option to select older versions of Unity,Required Unity Version Not Listed for Download in Unity Hub

I need to download Unity 2019.4.5f1 for Linux to support a particular project but Hub only makes the latest LTS version available and I cannot find any Linux download pages, only Windows and MAC.,I need to use Unity 2019.4.5f1 for Linux to support a particular project. Hub only gives the options for the latest 2019 build and I cannot find a link for downloading Linux versions, only Windows or MAC. We are developing in Ubuntu 20.04.