DoomEd was a program written by Carmack and Romero in 1993, to directly build the levels from the original Doom. Twenty seven years later, the developers behind Twilight Edge Software are releasing a free and independent port based on that program, appropriately called ReDoomEd, which is based on DoomEd's source code, publicly released by John Romero himself on 2015.
Here you can see a video showing ReDoomEd running on Linux:
At a personal level, I remember experimenting on DoomEd a long time ago, and I actually managed to create a massive Doom level that is stored on a floppy disk somewhere... waiting for one day to be polished to current standards and published. The first weeks I had a love-hate relationship with this editor, because when compiling the level sometimes it crashed or due to the technical limitations of the time I wasn't able to implement all the features I wanted, but after some insistence I managed to overcome these problems and succeed. They were highly rewarding moments, and I remember being genuinely happy about it; because of these memories I'm totally confident to say that everyone should create a level or add-on at least once in their lifes. The joy of exploring a world that you created from scratch simply cannot be described, only experienced.
Besides, as of 2020, there is still a strong demand for new levels on the Doom community, and people across the years released absolutely masterpieces that are honoured on a yearly celebration called the Cacowards (an obvious reference to the legendary floating demon). And obviously, let's not forget the release of the effective SIGIL (GOL articles here) just a few months ago, which had a very positive reception as well. You really can say Doom is eternal, if you think about it...
Here are the links for the install scripts for Debian based-distros and for Fedora. Don't forget that you need to download either Zandronum or GZDoom to be able to play Doom on Linux. Also, you will need a copy of the original games, because nothing can be done without the .IWAD files - you can find Doom easily on GOG.
And finally, just keep in mind DoomEd was limited to the vanilla version of Doom. There are already newer Doom editors out there; I can mention PrBoom (although it was lastly updated more than a decade ago) and Eureka (which had its last update on 2018), which might have new capabilities and functionalities; even Romero mentions some limitations on one of his tweets, but still ReDoomEd theoretically may be a good place to start before moving to more advanced features.
I will most likely cover these two other editors on another article, provided I have the time to do so, but in the meantime feel free to create your own Inferno...