To get faster steam downloads in linux:

create ~/.steam/steam/steam_dev.cfg and add:

@nClientDownloadEnableHTTP2PlatformLinux 0  
@fDownloadRateImprovementToAddAnotherConnection 1.0

restart steam, start a download, and you should notice a better download rate.

for me it went from capping at 100mbps to now going 500+mbps like it should.