I'm having the same. Using it on a MacBook Pro 16-inch, 8-core i9, 64GB RAM and a 1TB SSD, running macOS 11 Big Sur (developer beta 4). How long do you reckon the indexing to take? I've found the following for Safari.app. It has worked in the past on the exact same configuration, using Alfred 4.1.1.
Check mdls file metadata...
❌ Metadata missing essential items
kMDItemFSContentChangeDate = 2020-01-01 08:00:00 +0000
kMDItemFSCreationDate = 2020-01-01 08:00:00 +0000
kMDItemFSCreatorCode = ""
kMDItemFSFinderFlags = 0
kMDItemFSHasCustomIcon = 0
kMDItemFSInvisible = 0
kMDItemFSIsExtensionHidden = 0
kMDItemFSIsStationery = 0
kMDItemFSLabel = 0
kMDItemFSName = "Safari.app"
kMDItemFSNodeCount = 1
kMDItemFSOwnerGroupID = 0
kMDItemFSOwnerUserID = 0
kMDItemFSSize = 1
kMDItemFSTypeCode = ""
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❌ Troubleshooting failed
