I used to be able to select and edge loop with AltRMB and then just continue with ShiftAltRMB. But this no longer works in Blender 2.80 and nightly builds of 2.79.
Is there another way to achieve the same?
It's not related to the nightly builds since I am also experiencing the same with the latest official release. Deleting Blender's user preferences doesn't change anything, nor does resetting the keymaps.
So it might be related to the Linux distro I am using (elementary OS), I'll have to look into that and follow up here as soon as I found something.
In the meantime, I switched back form elementary OS to Pop!_OS, which resolved the issue. It seems that somehow, elementary OS was blocking the ShiftAltRMB combination. The issue persisted with all versions of Blender, be it 2.79 official, 2.79 nightly or 2.80. Now, all is fine. Even 2.80 works as expected.
As of now, Blender 2.80 is using left-click by default for selecting. Selecting edge loops is done by double clicking, which is so much more convenient.