My ubuntu is Linux kubuntu 5.3.0-40-generic
and via apt update I still get
gnucash Build ID: 3.7+(2019-09-07)
It's online banking tool is not compatible with the new crypto procedures of German banks.
From https://packages.ubuntu.com/search?keywords=gnucash:
focal (gnome): personal and small-business financial-accounting software [universe]
1:3.8b-1build3: amd64 arm64 armhf ppc64el s390x
So you'll get it when Ubuntu 20.04 LTS is released in late April 2020, tentatively on April 23.
Alternatively, if you don't mind using a ppa in 19.10, search Launchpad for gnucash ppa. One example is https://launchpad.net/~sicklylife/+archive/ubuntu/gnucash?field.series_filter=eoan.
2020-04-20 - GnuCash official version is still missing from Ubuntu Software centre for Ubunutu 20.04, there is a branched version which appears to be of older with less functionality. However GnuCash 3.8 is available in Kubuntu 20.04 software centre. Kubuntu 20.04; KDE Plasma Version: 5.18.5; Kernel version: 5.4.0-37-generic OS: 64 bit