Performance was already poor in v115, but has gotten much worse since upgrading to 128.5. This is a documented bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1906482 Are there any known workarounds? If not, how can I downgrade with losing all of my settings? I have 7 e-mail accounts and a few calendar accounts set up. This took a lot of time, since several of them require app-specific passwords. Thunderbird complains if I try to open a profile from a newer version in an older version of the software. How can I do this safely?