Ukuu isn't properly installed on Ubuntu 16.04.6 LTS. The package isn't installing the .desktop file to usr/share/applications/ or any of the doc/po files at all. A comparison of the file lists between 16.04 and 18.04 can be seen below. This doesn't happen on any other revision of Ubuntu tested.
When installing any new kernel, the install gets as far as determining which kernel is already installed before recursing and doing the same again - opening a new TerminalWindow in the process. This happens infinity.
Operating System: elementary OS 5.x (Ubuntu 18.04 LTS)
Whenever the TerminalWindow closes, the 'Booting previous kernels' message appears immediately after - regardless of whether you've just successfully installed a new kernel or not. This is especially annoying when multiple TerminalWindow instances open during the installation process.
This message should only be triggered after a successful kernel install, and after the last TerminalWindow closes and focus is given back to the MainWindow.
Operating System: elementary OS 5.x (Ubuntu 18.04 LTS)