I'm not a TV user, so I had missed this unfortunate development... I went earlier on the official site to fetch and archive an installer of the last Vista compatible TV version, where I found the following notice:
https://community.teamviewer.com/t5/Knowledge-Base/Which-operating-systems-are-supported/ta-p/24141
Unfortunately, the latest version is v15 (15.2.2756 to be exact) and I have confirmed it doesn't launch under Vista (due to missing function calls in Vista's system files... ); so, the last Vista compatible version, v14.2.x, can't be used anymore with a free licence...
But even if you pay for a commercial licence, there are limitations:
Sunsetting active servicing of operating systems
That previous link suggests going to
https://www.teamviewer.com/en/download/previous-versions/
for a v14 download; v14.7.13736 is displayed there (???); I am using NM28 and my UA does advertise my Vista OS (NT 6.0); the link to the installer is
https://download.teamviewer.com/download/version_14x/TeamViewer_Setup.exe
Upon clicking that, it redirects to
https://dl.teamviewer.com/download/version_14x/14.2.56673/TeamViewer_Setup.exe
which suggests a v14.2.56673 is the last Vista compatible TV version; however, it is impossible for me to complete the download, the browser generates an error, the wording is "The page doesn't redirect correctly" (translated from Greek); what gives?
The portable download link
https://download.teamviewer.com/download/version_14x/TeamViewerPortable.zip
simply fetches v14.7.13736, which I confirmed doesn't launch under Vista... ; at last, I was successful in fetching the portable version of TV v14.2.56673 via the following, manually composed, link:
https://dl.teamviewer.com/download/version_14x/14.2.56673/TeamViewerPortable.zip
... and I confirmed v14.2.56673 (portable) does successfully launch here (be it only after a considerable while since the main executable is double-clicked):
... But, the installer of v14.2.56673 is still a no-go for me...
... And do you want to know how I ended up getting that one? By requesting version 14.2.8352 (!) ; yes, the link (manually composed):
https://dl.teamviewer.com/download/version_14x/14.2.8352/TeamViewer_Setup.exe
will fetch: How MAD has this world become?