In response to your request, Henix is about to meet your need for a compatibility of Xsquash with Jira Cloud. Indeed, Squash's development team is planning to release an evolution of its Xsquash4Jira plugin (see the info box below) for early 2020. It will be possible to use Xsquash with projects hosted in Jira Cloud as you can currently do with projects hosted in Jira Server.