You can try the method here: http://ubuntuhandbook.org/index.php/2020/07/install-gnucash-4-0-ubuntu-20-04-18-04/
I recommend that you first remove your existing GNUCash using Synaptic before trying those steps.
You can try the method here: http://ubuntuhandbook.org/index.php/2020/07/install-gnucash-4-0-ubuntu-20-04-18-04/
I recommend that you first remove your existing GNUCash using Synaptic before trying those steps.