Strange… I, just a few days ago, managed to get it running on Ubuntu 16.04 without any issues.
Did you ensure you installed the dependencies here: A new, community-hosted Unreal Engine Wiki - Announcements and Releases - Unreal Engine Forums
When I tried first time around, the setup.sh failed and I thought to myself why not just try do that step even though it says it’s not the supported method since 4.9. Did that and it worked afterwards. I believe one of the listed dependencies did not install on 16.04 when I did it, but I was still able to build with no issue by just skipping that one and installing the remainder of them. (cant remember what it was or if it was important)
Check those and run setup.sh again, it should say successful or something like that at the end? You definitely cannot progress unless it does.
As for the Marketplace, sure. The launcher doesn’t work but you can access all the content from the website (see marketplace link in top banner)
For me, I’ve gone back to windows which sucks but I’m starting to hit that age and just too busy to spend half my time trying to get little things working properly. I try linux every year or 2 and it’s come a very long way and so very close to being my only OS, but there is still that barrier for people like me, I just want to be productive these days, not spend time tweaking or getting things to work just right.