You could try to start
Thunderbird with the "safe-mode" option by entering in the terminal
thunderbird -safe-mode, which sometimes allows one to start the program when it won't start normally. This is effectively a debug mode which makes
Thunderbird start without addons disabled and with only the most basic configuration options enabled.
Alternatively, you could find your
.thunderbird folder in your home folder by viewing hidden files in your file explorer. Then you should be able to navigate to the various folders, although you won't be able to access the stored passwords as they are kept encrypted in sqlite databases. So backup your profile first if you want, then navigate to
.thuderbird/<profile.default>/ then delete
key3.db to remove your passwords and logins. This only removes the passwords, but it will be enough to get
Thunderbird running again if my first method fails.