Install Doom Editing Tools
I use both Slade and Eureka on Ubuntu 18.04.
The current Eureka supports (G)ZDoom features, including rendering of 3D floors and slopes. The 3D mode displays both of these correctly. It does not support UDMF however. It will allow you to write ACS scrpts, but NOT compile them. For this I use Slade. Slade is better for resource editing but does also have a map editor, but this does not display 3d floors. Slade does however compile ACS scripts as long as a BSP builder is configured.