Commenty, BugHerd, Mantis Bug Tracker, zipBoard, not8, Usersnap, Userback, ProjectHuddle, Visual Inspector, Survicate, Marker.io, TrackDuck, BugReplay, Ybug, Pangolin, Bug Snapshot, FeaturePeek, qTrace, ReportBugz, Bugyard, Flowcast, InSite Feedback, Zinputs, DebugMe, Webscope are some alternatives to Timeline.io.