I have got an old Mac whose latest compatible operating system is up to 10.11 El Capitan. I noticed that the highest compatible version for El Capitan is 15.2 on Which operating systems are supported?, however, I didn't find where the 15.2 version is for downloading. The article says here is for downloading, but only 14, 13, 12, 11 and 10 is available, no 15.2
Is 15.2 version available on the official website?
In addition, I downloaded the TeamViewer of 15.2 from other website on a new Mac. Atfer installing on the new Mac I just directly copied the TeamViewer of 15.2 to that old Mac, but still could not be opened:

Hopefully the reason was that it was from other website, not official website. Otherwise it still won't run on El Capitan even though TeamViewer of 15.2 is available on official website.
Is the latest compatible version of TeamViewer on El Capitan really 15.2?