Presently it is not possible to download assets (e.g. plugins) from the Marketplace via Linux due to a proprietary URL scheme employed by the marketplace website that is only recognised by Windows.
This is a showstopper for all Linux-based developers.
Work around atm I use it to install the Epic Games Launcher in Lutris and use it that way, Window UI is buggy but the main parts of the launcher work, heck can even run UE4 Windows in Lutris but again UI is buggy but viewport is smooth.