Thunderbird opens a small text file, profiles.ini to get the name and location of the profile.If the file named in the profiles.ini file does not exist, that error is produced. Locate the Thunderbird folder to see the profiles.ini file. With thunderbird not running, you can manually edit the file to point to the proper profile. I am not well-versed in Linux, so can't give detailed suggestions.

I have the same problem as david, i.e. not knowing where Thunderbird is supposed to store the profile data in your case, but mainly because I'm not sure whether you installed some version of Thunderbird that might use a different location for that…

And are you telling us everything you did regarding Thunderbird? Because this looks like you're omitting something relevant you also did, such as deleting a profile folder from the Thunderbird Profiles folder…

Nope, that's all there is. Installed new OS, installed Thunderbird, it does not start up.

Use the following article to try to figure where the Thunderbird folder is located in your filesystem. You'll know you've found the right folder when you see a profiles.ini file and a Profiles folder in it: https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data

If this is a new installation, you may then bypass that blocking error message as follows:

1. Quit Thunderbird if it's running.
2. Delete profiles.ini.
3. Launch Thunderbird. Instead of looking for a profile folder that apparently doesn't exist, it will create a new profiles.ini file with a new default profile and will let you proceed.
4. You will be asked to set up a mail account, but you don't have to. If you have a profile folder that you copied from another computer and want to use that instead, you may cancel the account setup process and choose the option to Use Thunderbird without an email account when asked for confirmation.
5. Choose Help > Troubleshooting Information from the menu bar.
6. Click about:profiles in that page to open the About Profiles built-in Profile Manager.
7. Create a New Profile, read the introductory text if this is new to you, then click Continue.
8. Click Choose Folder and choose the profile folder you brought from the other computer. This is where the profile folder is linked to an actual profile.
9. Name the profile however you want and click Done. You have now associated the profile folder with an actual profile that Thunderbird knows about.
10. The new profile may have already been set as default. If not, use the Set as default button under it to make it so.
11. Click Launch Profile under the new profile to start using it.

The help articles I read did not help. I uninstalled Thunderbird. And installed again. It works now.

I had the same very annoying issue after upgrading from Ubuntu 22.04 to 24.04.2. Quickly figured that Canonical and/or Mozilla must have messed up access to the profile data in its wonderful forced migration from apt-based to snap-based installation of Thunderbird.

Looks like that least part of the reason why that automatic migration went wrong was that I had made ~/.thunderbird/ a symlink to some other directory: ~/.mozilla/thunderbird, and for some silly reason the migration did not cope with that.

Fixing this issue cost me several hours of trial and error. What did the trick in the end was:

• exit Thunderbird
• move the original ~/.thunderbird directory with all its contents to ~/snap/thunderbird/common/.thunderbird
• in each profile, update all directory references in pref.js accordingly
• restore the mail folder files from a backup as far as possible
• re-start Thunderbird, which then updates/re-fills the mail folder files via IMAP

See also https://askubuntu.com/questions/1528666/thunderbird-upgrade-to-snap-24-04-1-wont-open-with-original-profile-how-t/1543775#1543775

For me this helped. Go to https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data and a described there, open a terminal to start the profile manager. Choose one of the options - I believe it was the upper one in my case - and then press 'start Thunderbird' and see what happens. If you still get 'can´t find profile folder or it's missing' (something like that) try another option. In my case Thunderbird eventually found the profile-back-up I created with an add-on within Thunderbird before I migrated to Ubuntu 24.04. Maybe the manager finds the official zip-file for backups too. I have you have the same luck!

Edit: what a shame that Ubuntu fails to properly reinstall the profile into the new Thunderbird! And it won´t even start without it! Now people who trust in the company and depend on their e-mail are lost.