Noctis IV is an old DOS game, or perhaps more of an art project about flying through a galaxy and exploring (sections of) planets on foot. Notably, you can name stars, planets, and place markers with notes on planetary coordinates, and then you can share those with other players via an "INBOX" system. While it technically has even less gameplay than NMS ever did, its primitive but custom 3D engine produces absolutely striking landscapes to explore [0]
While the author's webpage seems to have died at some point in the recent years, the project lives on through two community made mods, Noctis IV Plus [1] and Noctis IV Community Edition (NICE) [2].
[0] https://mooses.nl/nice/screenshots/city2.gif