libgpuarray has been de facto abandoned upstream since 2018, and is
currently unused in Debian. (Its original user was theano, which was
removed in #1042574.)
It currently has what may or may not be a wrong-answer bug (#1031414),
and two broken-by-transition bugs. (The latter two _might_ be easy to
fix - I haven't tried because I've already mostly given up on it.)