https://www.archlinux.org/packages/community/x86_64/openmoti... lists as being updated 2020-01-05, and https://sourceforge.net/p/cdesktopenv/wiki/SupportedPlatform... claims that CDE supports a rather lot of platforms (which implies motif), although I'll grant that most of those probably haven't been tested in a while.
https://www.archlinux.org/packages/community/x86_64/openmoti... lists as being updated 2020-01-05, and https://sourceforge.net/p/cdesktopenv/wiki/SupportedPlatform... claims that CDE supports a rather lot of platforms (which implies motif), although I'll grant that most of those probably haven't been tested in a while.