We looked at Linear and other options but ultimately ended up going with Shortcut. We wrote our own small migration script and moved over the old Pivotal IDs to keep as much historical context as we could. Shortcut's been a good tool overall, though I preferred Pivotal's Goldilocks level of compactness as far as the UI was concerned, as well as the general design.
Pivotal's API was tidy and integrated nicely into our development process. We have some git aliases such as `git start <branch>` where the branch name will end with a story ID by convention. The alias would do the work of creating the branch, setting the remote to the dev's fork of our repo, marking the story as started, and assigning the dev as the owner. It saved a lot of manual steps, so thank you for your involvement in the project which allowed such a nice workflow!