How to deauthorize computers if no longer have access and no current computer running Apple TV

I tried to install Apple TV on my PC and got a message that I already had 5 computers authorized and need to deauthorize at least one. These must be former, long-gone computers since I don't have a current computer with Apple TV on it. I don't recollect ever deauthorizing a computer which is undoubtedly the problem. The instructions to implement Deauthorize All start with opening Apple TV (or Apple Music, which I don't have). What do you do with you don't currently have any computer with Apple TV and the ones that are authorized are long-gone? I do have iTunes installed on one computer, and it is authorized, but it doesn't give me the option to Deauthorize All, just to Deauthorize the current computer, so that doesn't help with the long-gone computers.