Cancelled BitLocker setup before setting a key: Windows says filesystem is unencrypted, Linux won’t mount it

I’m trying to help troubleshoot a Windows system for which BitLocker setup was started, but — upon discovering that TPM-backed key storage wasn’t available without switching to UEFI mode — cancelled. Windows claims that the filesystem is plain NTFS. Running Get-BitLockerVolume in PowerShell claims that no BitLocker volumes exist. However, if I boot into Linux…

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