Hi I have installed Thunderbird 68.10.0 on Ubuntu 20.04 - I needed this version to migrate from Mac to Ubuntu So going forward how do I update and upgrade Thunderbird (whilst retaining all my data etc) firstly to V68++ and towards V78.xx Many thanks

Just to add that the following does not provide any updates:-

Help | About Thunderbird

sudo apt update sudo apt full-upgrade

Updates from 68 to 78 that are prompted by TB's internal update process have not yet been deployed, due to several unresolved issues. That doesn't stop users from updating manually, but it's not recommended unless careful attention is paid to profile configuration and data migration. It's recommended to wait until Ubuntu releases the update and it's performed from within TB.

Ok, understand and I shall wait

hopefully migration path from 68->78 be available soon :-)

Updating to 78 for now is best left to tinkerers and DIYers. Just to give you an idea, here is a list of bugs in 78:

https://bugzilla.mozilla.org/show_bug.cgi?id=1644037