The best alternatives to Shrink for Github are Gitscout, Cashew, and GitHub Issues Solved. If these 3 options don't work for you, we've listed a few more alternatives below.
Sweetjab combines teams issues and pull requests from GitHub, into a single page, to easily prioritize and delete. Your organization is automatically being loaded into Sweetjab, and is always up-to-date with the changes made in GitHub.
Zokyo is a free to use chrome extension for GitHub developers. With Zokyo's extension, developers will be able to view all their assigned issues, edit any issue, add new issues to their repos, and go to each issue all from one UI accessible from any page.
HubDesk lets you receive and respond to emails with Github issues. HubDesk creates issues for each new inbound email thread and you can respond to the sender with an issue comment that starts with **@reply**. It can be used for bug reports or as a help desk.
A GitHub App/Action that automates the creation of issue branches (either automatically after assigning an issue or after commenting on an issue with a ChatOps command: /create-issue-branch or /cib).