Shadow of the Wyrm
Shadow of the Wyrm is an open-source, traditional roguelike. It had its first release in 2015, and typically sees updates every few months. More information can be found at shadowofthewyrm.org, or itch.io.
Quinze is a simple, curses-based 15 puzzle. It's meant to be built and played in Linux.
Martin's Dungeon Bash
The latest version of Martin's Dungeon Bash by Martin Read doesn't compile by default on Linux due to compiler warnings-as-errors. If you're interested, I host a copy of the latest sources patched to fix the warnings.