Of specific note, is the build designation in the SoftwareUpdate - 20A5343i versus the ADP versions ending in a w.
dru_satori
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Further Information that may be of value: The underlying error
Current device configuration requires an alternate installer to perform the update.: [com.apple.MobileSoftwareUpdate.preflight.error(Preflight):12|Unknown Error Indication|]" UserInfo={SUMacControllerErrorIndicationsSummary=|Unknown Error Indication|, SUMacControllerErrorIndicationsMask=8, SUMacControllerErrorIndicationsDescription=-> Current device configuration requires an alternate installer to perform the update., NSUnderlyingError=0x127605c60 {Error Domain=com.apple.MobileSoftwareUpdate.preflight.error Code=12 "The base build is not compatible for this install method." UserInfo={NSLocalizedDescription=The base build is not compatible for this install method., NSLocalizedFailureReason=The base build is not compatible for this install method., MSUPreflightAlternateInstallerRecommended=true}}, NSDebugDescription=[SUMacControllerErrorPreflightPrerequisiteCheckFailed=7722] Failed to perform PreflightPrerequisite operation: com.apple.MobileSoftwareUpdate.preflight.error(Preflight):12 | The base build is not compatible for this install method.
Suspect that it has to do with going from the base install to Beta 4, and the preflight is failing.
Digging deeper, it appears that though Software Update is showing this available to the DRK hardware, it does not include DTK required assets.