  We study quantum SU($M$) spins with all-to-all and random Heisenberg exchange
interactions of root-mean-square strength $J$. The $M \rightarrow \infty$ model
has a spin liquid ground state with the spinons obeying the equations of the
Sachdev-Ye-Kitaev (SYK) model. Numerical studies of the SU(2) model with
$S=1/2$ spins show spin glass order in the ground state, but also display SYK
spin liquid behavior in the intermediate frequency spin spectrum. We employ a
$1/M$ expansion to describe the crossover from fractionalized fermionic spinons
to a confining spin glass state with weak spin glass order $q_{EA}$. The SYK
spin liquid behavior persists down to a frequency $\omega_\ast \sim J q_{EA}$,
and for $\omega < \omega_\ast$, the spectral density is linear in $\omega$,
thus quenching the extensive zero temperature entropy of the spin liquid. The
linear $\omega$ spectrum is qualitatively similar to that obtained earlier
using bosonic spinons for large $q_{EA}$. We argue that the extensive SYK spin
liquid entropy is transformed as $T \rightarrow 0$ to an extensive complexity
of the spin glass state.
