A preview version of Unreal Engine 4.21 is now available, with it there's lots of improvements to many areas and it has a few Linux additions too.

Overall, it seems like a pretty good step up for Unreal Engine with a lot of new features, bug fixes and general code cleanups. It has improved IPv6 support, improvements to DDoS Detection and Mitigation, experimental support for the SteamVR Input subsystem, improved performance of the Unreal asset cooking process, loads of animation system updates and the list goes on and on.

As for the Linux-specific improvements, there's not many but they will probably be rather helpful:

Linux Platform Get Media Player - From 4.21 on, you can use bundled WebMMedia plugin to play back .webm VPX8/9 videos.

Linux Crash Report Client Has a GUI - They've added support for the Crash Reporter GUI to now pop up when a crash occurs. Which should help improve feedback.

I've seen a few developers have troubles with video playback in Unreal Engine on Linux, so hopefully with this it will help future UE native ports.

See the full list of changes here.