given you have an addon installed that affects the composer, I suggest restarting in troubleshooting mode from the help menu and see if that might be the cause.

Matt, sorry I forgot to mention I confirmed it also happens in a freshly installed 128.1.0esr in Ubuntu 22.04 with no add-ons. This was NOT happening in prior versions of Thunderbird. I can't imagine why I'd be the only user seeing this behavior.

given you have an addon installed that affects the composer, I suggest restarting in troubleshooting mode from the help menu and see if that might be the cause.

Can you please just do it.

You might not be the only one, but as Linux represents less than 2% of Thunderbird users, and Ubuntu only a fraction of those, finding someone else is a little like that needle in a haystack.

Restarted in troubleshooting mode with all add-ons disabled and the issue persists.

Upgraded to 128.1.1esr and the issue persists.

Re: 2% are you saying the Thunderbird QA team does not test the Linux version?

I was able to solve the problem using Flatseal giving Thunderbird access outside of its sandbox to specific folders such as ~/Pictures, etc.

This info should be added to the support article: Installing Thunderbird on Linux

Sure, get with it anytime you like. https://support.mozilla.org/en-US/kb/installing-thunderbird-linux/edit

Submitted my edit and happy to contribute to Thunderbird again!