This unfortunately doesn't tell us which install method you chose, nor which version of Thunderbird you are using.

Thunderbird is telling me it is the 128.2.0esr (64-bit) version (and, at the time of writing, up to date). I installed following the steps on the Installing Thunderbird on Linux page with the heading "Installing Thunderbird manually (For advanced users)": I downloaded the .tar.bz2 file (stable release, I believe), unpacked, moved, created the link, and downloaded the desktop file. Hopefully I have now supplied all the wanted information.

I solved the problem by doing what was suggested here.

- Open a terminal and then type "cd /usr/local/share/applications/" (without quotation marks) - Open the thunderbird.desktop file for editing: "sudo nano thunderbird.desktop" - Add "StartupWMClass=thunderbird-esr" in the [Desktop Entry] section. - Hit <control>+<O> to write the changes to the file. - Hit <control>+<X> to exit nano.

On my system, the gear icon disappeared immediately and the Thunderbird icon started working as it should.

This worked for me. I had the same issue after clicking on a distro upgrade from Ubuntu 22.04 to 24.04.

Thanks,

Spiderverse