When you say "While I don't work on those apps, I'm not aware of any client requirement for administrative access to be enabled on the Web Adaptor. Can you point me to the doc that says that?"
Not at the moment. It may be a legacy thing from earlier (like 10.6) releases.
I think for our org the main reason we set up admin access through the web adaptor was so that we could access Server Manager while not on our internal network by going through the F5 and the portal user store in case of emergencies - like hurricanes - and I was not on network or could not be on network but still need access to Server Manager.
I don't have a staging environment and don't want to try something like this on the fly. You said earlier that:
"We addressed this in 11.0, but used an incorrect method, which looks for any character in the URL that matches any character in "admin". In your case, https://ags3.our_org.net/agsfed/admin/ all of the bolded characters are characters in "admin", therefore got stripped from the URL"
Well, I say that this is a bug and needs to be addressed - because it has only shown up at this very latest release. Don't get me wrong - I really appreciate your insight here.
As always, I poured through the issues addressed
https://downloads.esri.com/support/downloads/other_/110-IssuesAddressedList_07192022.pdf
and all of the 'what's new' and saw nothing about this, even in the 'Disaster Recovery' section of the document.
I'm just not sure I can change the admin access - and if something goes wrong and re-enable it, that when I do re-enable that the site will still validate, what will the impact to Monitor be, etc etc.
Thanks again - I'll have to give this more thought and will post back