Yes, both Phabricator and Assembla offer a Free Trial.
Phabricator is designed for Medium Business and Small Business.
Assembla is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Phabricator Starts at $20/User/Month whereas for Assembla Starts at $9.16/User/Month.
Some top alternatives to Phabricator includes Jira, Assembla, Jira Service Desk, GitHub, GitLab, Qualified, AnalyticsVerse, Workvivo, CodeSee, SaaS Forge, GetGit and Bitbucket.
Some top alternatives to Assembla includes Quickbase , Smartsheet, ClickUp, Zoho Projects, Jira, Wrike, TeamGantt, GitScrum, Teamwork, ProjectManager.com, Backlog, Axosoft, TaskBranch, Quick Base, Project.co and Height.