By far and away, linear.
The task tracking features you actually use, it’s fast, you don’t waste a billion years playing “who knows how to do this and has the permissions hell” that you would with Jira. The integrations work properly. The layout and UX makes sense, and all the nontechnical people I’ve used it with liked it and had no issues with it.
Linear is quite seriously one of the best products (in any category) I’ve ever used.
They have a first class MCP server, and you can basically run a project from your agent. Implementing something, and you find out there's more to do later on in a separate issue? Agent creates the issue for you and off you go. It works very nicely, and also has a great UI but I mostly using it from my agent.