ActivityWatch/activitywatch: The best free and open-source automated time tracker. Cross-platform, extensible, privacy-focused.
Cool open source time tracking software. Still pretty rough around the edges and needs a lot of polish before I can use it effectively. One thing that I need that this doesn't have is syncing across devices, but it does support macOS, Windows, and Android, which is more than I can say for some other time trackers (e.g., Rize).