ISDCF has conducted plugfests over the years and has gathered test material that might be helpful.
We post these to https://isdcf.com/ISDCF/test-content.html .
3D subtitle Tests: 3d_stereo-comparison-test_smpte_nov-2015 (From Jim W)
Frame rate tests: https://dci.foxpico.com/basic/plugfest/fox-format-tests-hfr-20160510.tar
DTS-X content: INSTALL_CK_01-MDA11031-150324.zip
Go to https://dci.foxpico.com/basic/plugfest/2014-Feb/ to get content used at the February 2014 plugfest