Hello

Take a look at https://connect.mozilla.org/t5/discussions/calendar-search-function-in-nebula/td-p/63744

You can use Betterbird which has restored that functionality. https://betterbird.eu/releasenotes/index.html

Otherwise https://bugzilla.mozilla.org/show_bug.cgi?id=1855900#a25670468_29811

Otherwise Revert the update, take a look at https://connect.mozilla.org/t5/discussions/forced-update-to-thunderbird-nebula/m-p/65304

Hello Take a look at https://connect.mozilla.org/t5/discussions/calendar-search-function-in-nebula/td-p/63744

I am familiar with that discussion. Which part of it do you want to draw my attention to?

You can use Betterbird which has restored that functionality. https://betterbird.eu/releasenotes/index.html

Thanks. I considered that but stumbled over the notice in the release notes:

Note that Thunderbird 128 and hence Betterbird 128 is shipping with a broken backend causing IMAP folder corruption under some circumstances. [...] Hence version 128 SHOULD NOT BE USED IN PRODUCTION!!

So I would really, really prefer to return to version 115. Hence my question.

See Also: → https://bugzilla.mozilla.org/show_bug.cgi?id=1855900#a25503094_29811

About So I would really, really prefer to return to version 115. Hence my question. See Also: → https://connect.mozilla.org/t5/discussions/forced-update-to-thunderbird-nebula/m-p/65304/highlight/true#M23110

Agent virtuel said

See Also: → https://connect.mozilla.org/t5/discussions/forced-update-to-thunderbird-nebula/m-p/65304/highlight/true#M23110

Thanks. In my case, it is very clear what caused the update. It was my own imprudent action. No antivirus software or other external application involved. I'm pretty confident it won't happen again once I manage to downgrade. I have also managed to identify the previously installed version from Thunderbird's update history (115.13.0) and to download that version from ftp.mozilla.org. My only problem is how to actually do the downgrade without killing my profile.

Info https://www.ggbs.de/extensions/AllEvents.html

AFAICS the discussion about why I'd want to downgrade has been finished now. I would like to come back to my original, as yet unanswered question: How can I downgrade from Thunderbird release 128.1.0.esr "Nebula" back to release 115.13.0, ideally without losing my user profile?

You should find this is fixed in 128.2.1.

Regrettably, no. After upgrading to 128.2.3 esr (I never got offered 128.2.1) calendar search doesn't work at all anymore. Independently of that, my question remains: how can I undo an upgrade, ie. revert to a previous version of Thunderbird?

Not sure it was mentioned before: I used https://archive.mozilla.org/pub/thunderbird/releases/ to pull an older version. My issues are the on-and-off handling of untrusted certificates, in 128.2.2esr and 128.2.3esr it seems to be broken... once more - or at least not as expected or the message popup that allows you to accept them does not show on my Windows 10 or whatever. Downloaded and installed 128.2.1esr into default folders and it works again. All config seems to be preserved. Switched off the auto-updates (which are annoying in their frequency anyways) and hopefully Thunderbird and myself will stay friends a little longer (and yes, I have to switch to a provider that provides proper certificates)

@reiner28: That may work when staying within the same major release, but not for going back from 128esr to 115esr.

Anyway, my calendar search works again. (The somewhat surprising fix was to find and delete all calendar entries that had an empty subject line.) So, with my immediate need for downgrading gone, I retract my question.