I build a ncurses distributed CRM system (that also have a web frontend). I use it for my consult business, with invoicing, event logging, todo lists, projects and so on.
I love a quick, keyboard driven application and I also have good codebase to use as a testing ground for CI/CD, code analysis etc.
Two weeks ago I actually got my first customer buying a license for it, after being in development for 9 years!