After an unfortunate Arch update, udisks2 seems to be broken and never respond via DBus.
Running solid-hardware5 list details takes for ever and at some point tells me:
Failed enumerating UDisks2 objects: "org.freedesktop.DBus.Error.TimedOut"
"Failed to activate service 'org.freedesktop.UDisks2': timed out"
A quick glimpes at the udisks2 backend and it looks like Solid makes blocking calls instead of using a dbus pending watcher or something.
solid uses the synchronous QDBusInterface which is should not nowadays.