The museum is, but the online resources are still up. Some of the machines are running on emulators - I remember the CDC 6500 chiller died sometime in the first year of the pandemic and the machine had to be turned off until repaired.
I hope it gets enough funding to reopen after the apocalypse is over.
In any case, this guide is wonderful for using Hercules with VM/370 and MVS 3.8j.