Jira entered the existing market of tools for project management, providing those companies and entities with the tools necessary to efficiently manage internal workflows. On their website they highlight their personal strengths in comparison with other popular competitors.
Linear is focused on the resegmented market. Their tools are primarily for product development, but with a specific focus on software teams building at a rapid pace. The intent is that with a focus on software teams, it is a smoother and sleeker experience for users aiming to augment their product development. One noticeable competitor of Linear is Jira.
Productboard, however, has entered a new market, primarily one that focuses not only on augmenting the product management and development process, but rather one that enables the process from start to finish. This is an end-to-end tool that supports businesses without requiring heavy product management progress before a company turns to this tool for support.
Sources:
https://www.coursera.org/articles/what-is-jira
https://www.atlassian.com/software/jira/comparison
https://everhour.com/blog/what-is-linear-app/
https://www.productboard.com/use-cases/
