What are some alternatives?
When comparing Pangolin and TrackDuck, you can also consider the following products
InSite Feedback - InSite Feedback provides instant feedback and reviews of your website.
Redmine - Flexible project management web application
UserSnap - Usersnap Track is your central place to organize user feedback and collect bug reports. One screenshot is all it takes. Get rid of endless email exchanges and coffee-stained sticky notes. Your new life is awaiting you!
GitLab - Create, review and deploy code together with GitLab open source git repo management software | GitLab
Webscope - Get live website feedback from your clients
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.