I’d personally argue that Sigil and Sigil II count as “official” since they were made by Romero, but I agree that Legacy of Rust is phenomenal. The new weapons are interesting and fun to use, and the new enemies, particularly the plasma trooper, are a blast to fight. Definitely recommend everyone try this.
Other sourceports are working on adding the ID24 features used by LoR, so it’s conceivable that it might be playable in DOS eventually.
