I had a hard drive failure on a secondary domain controller that also had a secondary adfs server setup. This took way longer to resolve than I think it should have. Here are the steps to remove the failed server.
On a working domain controller open Active directory Users and computers
Browse to the Domain controllers OU
Right click the server you want to remove and click Delete
Click Yes to confirm and then on the next prompt be sure to check the box that says:
“Delete this domain controller anyway. It is permanently offline and can no longer be removed using he removal wizard.”
Click Delete
Click yes to confirm deletion if it is a global catalog server
Next go to active directory sites and services
Delete the server in the server list you no longer need
I did not need to do the cleanup step but you can take a look at that option to make sure it is gone:
Next run this command to delete the old secondary ADFS server:
set-adfsFarmInformation -RemoveNode “server fqdn”
You can then type the following command to make sure it is gone:
Get-ADFSFarmInformation
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