We use TeX Live 2018 on our servers for new projects and copies of existing projects, which provides about 4000 packages, including:
fontspecthat require XeLaTeX or LuaLaTeX for unicode and font support.
For more details please see this blog post.
Existing projects use the TeX Live image that was current at the time the project was created, to prevent package updates from affecting existing projects. To update an existing project to our latest TeX Live version, you can make a copy of the project and continue working in the updated copy.
Also note that you can upload
.cls files for other packages, for example those from CTAN.