Unable to upgrade yahoo mail after installing Sonoma

restart your computer in Safe mode, and try the mail update while in safe mode.

"works in safe mode, fails in regular mode" Implies "it's something you added"

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners, Bit Torrent, or a VPN that you installed yourself. The main reason is that they are relentless in scanning your files, non-stop, looking for virus-like patterns in Everything, or looking for files that have changed. When completed, they do it all again.

<< Can’t configure complex emails setups in Sonoma >>

The issue appears to be Safari's "advanced tracking and fingerprinting protection". Go to Safari's Settings -> Advanced and uncheck "Use advanced tracking and fingerprinting protection".

Can't connect Gmail to Macmail (Sonoma 14… - Apple Community

Thanks bosmacs!