Eu não tive nenhum problema em criar a partir da fonte:
# Assuming you have basic build tools already installed
sudo apt-get install cmake libgcrypt11-dev
git clone https://github.com/keepassx/keepassx.git
cd keepassx/
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local
make 2>&1 | tee make.log
sudo make install 2>&1 | tee make-install.log