BAR is great – Total Annihilation was always one of my favorite games from childhood and BAR feels the most like it compared to other spiritual successors like SupCom/FA and other community projects. I actually tried to contribute a couple commits to the project but I don’t think they took them.
OpenTTD is fantastic. The graphics might give new players pause, but if you like building networks or logistical puzzles, or just like trains, it’s still one of the best in the genre.