i haven't seen 132.0.2. Did you download it from thunderbird.net? A possible approach is to download 132.0.1 from https://ftp.mozilla.org/pub/thunderbird/releases/132.0.1/mac/ and install over that. OR, this may work: Try:

   Exit Thunderbird if running.
   click windows key and 'r' key
   Enter: thunderbird.exe -P --allow-downgrade
   click on 'OK' 

If you got 132.0.2 elsewhere, such as a software site (e.g., majorgeeks), it is in your best interest to not do that. My suggestion may not work, but it seems all worked with 132.0.1 for you,

Thanks for trying to help.

I got 132.0.2 from the Mozilla site, <https://www.mozilla.org/en-US/firefox/new/> and clicked on the "download" link. That initiate downloading of "Firefox 132.0.2(2).dmg" (same name as the first time except for the (2) in the download name) and sent me to <https://www.mozilla.org/en-US/firefox/download/thanks/>

Installation of this newest download made no difference in behavior.

I've been searching for somewhere to get  Firefox 132.0.1 without success. 

I went to the ftp site you provided a URL for, which lands me in a directory with a huge list of sub-directories that I've no idea what to do with. Am I supposed to download all of those and then find some sort of installer? Suggestions welcome.

Your response focused on Firefox, the browser, and that may be confusing you. The directories in that link I sent all had the same version of thunderbird, but in different languages. I don't know your native language, so I sent the full list.

I successfully downloaded the English(US) version of Firefox 132.0.1 based on your guidance, and installed it.

Sadly, the problem remains. Apparently the core issue is with MacOS Sequoia 15.1.1 and at the moment I don't have a good way to roll that back to 15.1.0

I do have a three-weeks old "time machine" backup. So I'm going to save my work files from the past three weeks to a flash drive, then do a time-machine "restore" and go from there.

THANKS very much for your efforts at helping, the problem is clearly with Apple, who I've contacted.

I guess the lesson here is to be VERY careful with OS updates. Sigh...

I feel your pain. I know nothing of Macs, and don't know if you are better served with an OS rollback, or a thunderbird rollback. 132 is still in beta, and 115 may work (not that I would know). Here is a link to 115, English, if interested. https://ftp.mozilla.org/pub/thunderbird/releases/115.16.3/mac/en-US/ it may cause a message of thunderbird profile incompatibility. if so, look for a file named compatibilities.ini in the profile and delete it. I share this, but it may not work. but it should, if thunderbird is normally compatible with that release of the OS.