You can typically use a copy of the Windows profile "as is" under Linux since all settings that specify a location have both a relative and a absolute path version of that setting, and the relative path version (it specifies a location relative to the top of the profile directory) is always tried first. So the fact Linux doesn't support drive c:\ doesn't matter. 1. Help -> troubleshooting information -> open folder will open windows explorer at your current profile under Windows. Copy that directory to a usb/flash drive. 2. Start Thunderbird under Linux. It will automatically run the new account wizard, wanting you to add an account. Close that window. Use help -> troubleshooting information -> profile folder -> open folder to open whatever file manager you are using in Ubuntu at the current profile directory. When you started Thunderbird without a profile one was automatically created for you, though it has nothing useful in it. However, it is a legal profile that Thunderbird knows about and will use. Note: version 68 has only one open folder button (its for the profile folder). Version 78 has one for the update folder and one for the profile folder. That is why I provided a slightly different menu sequence for your Linux computer. 3. Exit Thunderbird (on your Linux computer) 4. Copy the complete contents of the old profile directory (on the usb drive) into the new profile directory (on your Linux hard drive). Don't copy the actual directory, just its contents. i.e. copy prefs.js over prefs.js etc. 5. Start Thunderbird again on your Linux computer. It should automatically find and use that profile. It doesn't care (or even know) that the contents have changed. 6. You will probably have to uninstall most of the installed add-ons since they are probably legacy add-ons. Version 78.* has NO support for legacy add-ons. Make certain that you keep a copy of your old profile (such as the one on the USB drive) for a while as a precaution.