Generally your would be best advised to wait until an upgrade is made available in your repository. However you can download it from the web site thunderbird.net. Generally the web site offer an appropriate version for your operating system. But if it gets it wrong go to the all languages and operating systems page https://www.thunderbird.net/en-US/thunderbird/all/ See https://support.mozilla.org/en-US/kb/installing-thunderbird-linux

Thank you. Guess I'll have to wait. Hope it doesn't take too long. JC