John Romero, one of the co-founders of id Software has revealed he's been working on SIGIL, a free megawad for the original 1993 DOOM.

From the official announcement:

SIGIL™ is a free megawad for the original 1993 DOOM® created by John Romero. It contains nine single-player and nine deathmatch levels. The free megawad will be released in mid- February 2019 and requires players own the original 1993 registered version of DOOM® in order to play. SIGIL™ is the spiritual successor to the fourth episode of DOOM®, and picks up where the original left off.

This is really fun, no doubt it will be quite popular especially with the rather large and active DOOM modding scene. Additionally, they're doing some limited edition fan boxes with Limited Run Games.

These boxes, will contain music from Buckethead, along with a custom song written expressly for SIGIL. A tempting purchase for any big DOOM fan, I especially love the sound of a 16GB 3-1/2-inch floppy disk-themed USB. You have until December 24, 2018 to order one and I imagine stock will go quite quickly.

Since it's a mod for the original doom, it should work in GZDoom for playing it on Linux like you would for other such packs.

See more on the official website.