By way of background, we have investment managers that protect their Acrobat PDF files with remote sign-in via a third party portal (Intralinks).

This used to be available until security settings via GP where set to block IE due to security issues.

My complaint is no different to others and it is very poor of Adobe to not have created a solution when Microsoft stated that IE was coming to end of life on June 15 2022. Leaving a fix to this issue so close to this date is very poor.

Do not close this case and say it is going to be fixed until it is. You just did this in my comment to Matts suggestion "Stop using Internet Explorer for application logins"
You have had almost 3 years to fix this and yet ....