For \"Get-Msoldomain\" powershell command-let I get the below output (lets call it Output#1) where Name, Status and Authentication are the property names a
Well, if you don't mind to take a little trip :) you can convert it to CSV which will force the string output, then re-convert it back from CSV to PS Object, then finally back to Json.
Like this:
Get-MsolDomain | ConvertTo-Csv | ConvertFrom-Csv | ConvertTo-Json