What is the largest, noncrystalline, non-polymer inorganic molecule?
I agree with the redditors that the answer is likely a polyoxometalate.
$\ce{Na48[H_xMo368O1032(H2O)240(SO4)48] · \text{ca.}~1000 H2O}$ aka
$\ce{\{Mo368\}}$ (core: $M \approx\pu{60.7 kDa},$ dimensions $\approx \pu{2.5 nm} × \pu{4.0 nm})$ is the primary candidate [1]:


Figure 2. Structure of 1a in crystals of 1 in polyhedral (a) and ball and stick (b) representation perpendicular to the $C_4$ axis and along the $C_4$ axis ((c) and (d); building units $\ce{\{Mo1\}}$ yellow, $\ce{\{Mo2\}}$ red, $\ce{\{Mo(Mo5)\}}$ blue with blue-turquoise pentagonal bipyramids; $\ce{O}$ atoms small red spheres, $\ce{S}$ atoms gray spheres).
Note that one capping part is turned against the other by $360/16^\circ.$
The different building blocks and the arrays of different local symmetry are assigned.

A recent review of mass-spectrometry studies of large polyoxometalates is also available [2].
References

Müller, A.; Beckmann, E.; Bögge, H.; Schmidtmann, M.; Dress, A. Inorganic Chemistry Goes Protein Size: A $\ce{Mo368}$ Nano-Hedgehog Initiating Nanochemistry by Symmetry Breaking. Angewandte Chemie International Edition 2002, 41 (7), 1162–1167. DOI: 10.1002/1521-3773(20020402)41:7&lt;1162::AID-ANIE1162&gt;3.0.CO;2-8.
Surman, A. J.; Robbins, P. J.; Ujma, J.; Zheng, Q.; Barran, Perdita. E.; Cronin, L. Sizing and Discovery of Nanosized Polyoxometalate Clusters by Mass Spectrometry. J. Am. Chem. Soc. 2016, 138 (11), 3824–3830. DOI: 10.1021/jacs.6b00070.