Since the 2020 version was made available, UnityHub on Linux does not display the latest 2019.3 beta (or RC since that was released yesterday) anymore. I cannot get any download link for Linux from the download pages and the UnityHub link does not work.
Is there any other trick I can try to get 2019.3.0 b11, b12 or RC installed on my Linux box?
Sorted. Looking at the Unity Hub logs I could see it was doing the right thing, but it took a couple of minutes until it opened the install dialog. This was running on a VM, so that may be the reason for the slowness.