Exchange search broken. Client search results don't return any hits after March of this year.

Exchange 2019 (15.2)

Indexing is running.

Get-MailboxDatabase | Format-Table Name,IndexEnabled

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Running a test search on a sample mailbox indicates search shows no output whatsoever.

Test-ExchangeSearch -Identity sample@domain

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And the search index status also seems to show that it isn't doing anything.
Get-MailboxDatabaseCopyStatus | fl Name,*index*

Creating a new session for implicit remoting of "Get-MailboxDatabaseCopyStatus" command...


Name                         : db01\EXCHANGE
ContentIndexState            : NotApplicable
ContentIndexErrorMessage     :
ContentIndexErrorCode        :
ContentIndexVersion          :
ContentIndexCrawlVersion     :
ContentIndexBacklog          :
ContentIndexRetryQueueSize   :
ContentIndexMailboxesToCrawl :
ContentIndexSeedingPercent   :
ContentIndexSeedingSource    :
ContentIndexServerSource     :

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Here is what I tried:

stop-service msexchangefastsearch
stop-service hostcontrollerservice

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Browse to the edb file path and delete the folder there named something like 9726BCE3-622C-4675-8A20-57BE574A5C9B12.1.Single
Remove all four directories that are located under the following folder: C:\Program Files\Microsoft\Exchange Server\V15\Bin\Search\Ceres\HostController\Data\Nodes\Fsis

cd C:\Program Files\Microsoft\Exchange Server\V15\Bin\Search\Ceres\Installer
.\installconfig.ps1 -action I -datafolder "c:\Program Files\Microsoft\Exchange Server\V15\Bin\Search\Ceres\HostController\Data"

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stop-service msexchangehm*
Get-Mailbox -Monitoring | Remove-Mailbox
start-service msexchangehm* 

start-service msexchangefastsearch
start-service hostcontrollerservice

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But no change.  Get-MailboxDatabaseCopyStatus | fl Name,*index* still shows "ContentIndexErrorMessage" and nothing else.