I needed the 2021 version of after effect today. spent 5 hours with adobe help today (on Twitter because they scrapped their agent chat system to get more money into the pockets of the shareholders). You can only install the past 2 versions 2022 and 2023. When i asked if they had an installer, Adobe, the makers of the software just shrugged and said 'we don't have it'.
I don't know how you concluded that the chat system was scrapped, it's very much up and running. Now regarding the installer for older verions, Adobe support is only your hope and since we have public download links for version prior to 2020 still working I don't buy that they don't have a link for 2021 to share. I think as @kglad mentioned you got connected to a wrong person who just didn't know or did not want to help. So try again and if denied ask to be connected to the supervisior.
To contact support follow the instructions given below 1. Go to https://helpx.adobe.com/contact.html?rghtup=autoOpen 2. Wait a bit on the page that opens up, it should automatically open a chat popup. If that does not happen then look for a call out/chat icon at the bottom right, click over it and the chat popup should open 3. In order to talk to a human type "AGENT" in the chat box 4. If you are not able to get to the chat window, then disable your adblockers, firewall, enable cookies/scripts on your browser. If it still fails then change your browser/machine/network.
P.S. Be mindful of answering anyone who sends you a private message. See the following for more information about scammers https://tinyurl.com/y7cfrr7y -Manan